&  <=\?>  —  W  i 


Digitized  by  the  Internet  Archive 
in  2017  with  funding  from 
Columbia  University  Libraries 


https://archive.org/details/radialbrickchimnOOalph 


United  Illuminating  Co.,  Steel  Point  Station.  Bridgeport,  Conn. 

Chimney  175'  x  12'  6".  Red  radial  brick.  Artificial  stone  trim.  Built  in  1921 
This  chimney  duplicated  at  the  same  plant  in  1973 
Foundation — reinforced  concrete  piles 

Wes  coll  r"  Xfapes,  Engineers 


Alphons  Custodis 
Chimney  Construction  Co. 


Radial  Brick  Chimneys 


95  Nassau  Street 
New  York 


CHICAGO,  ILL. 
PHILADELPHIA,  PA 
BOSTON,  MASS. 
ATLANTA,  GA. 
DALLAS,  TEX. 


Branch  Offices 

DETROIT,  MICH. 
BALTIMORE,  MD 
SEATTLE,  WASH. 
PORTLAND,  ORE. 
ST  LOUIS,  MO. 


PITTSBURGH,  PA 
CLEVELAND,  O. 
RICHMOND,  VA. 
MILWAUKEE.  WIS. 
MINNEAPOLIS,  MINN 


Custodis  Canadian  Chimney  Co.,  Ltd. 

TORONTO,  ONT.  MONTREAL,  P.  Q  VANCOUVER,  B.  C. 


3 


Copyright,  July,  1921 

Alphons  Custodis  Chimney  Construction  Co. 
95  Nassau  Street,  New  York 


4 


Foreword 

The  construction  of  every  chimney  presents  a  problem  of 
its  own.  In  the  following  pages  you  will  find  information, 
formulae  and  other  data  helpful,  even  when  not  exactly 
applicable,  in  the  study  of  most  chimney  problems. 

The  development  of  immense  boiler  horse-power  has  made 
necessary  tall  and  large  chimneys.  The  ‘unprecedented  in¬ 
crease  in  the  size  of  engines  and  turbines  in  the  past  decade 
and  the  consequent  increase  in  the  size  of  boilers  demanded 
the  use  of  these  large  chimneys. 

Each  of  the  five  specific  types  of  chimneys  generally  rec¬ 
ognized  require  calculations  in  twenty  or  more  fields.  This 
book  discusses  in  detail  all  the  factors  commonly  met  with  in 
chimney  problems. 

But  because  the  modern  science  of  chimney  construction 
has  not  yet  been  reduced  to  a  text-book  basis — -in  the  English 
language — the  practice  has  been  established  of  calling  upon 
chimney  construction  engineers  for  authoritative  information. 

This  book  is  published  to  furnish  engineers  and  architects 
the  data  essential  to  their  study  of  design  and  size  for  the 
general  chimney  requirements.  Views  and  designs  are  show  n 
of  chimneys  illustrating  most  of  the  known  requirements. 

It  should,  however,  not  be  assumed  that  all  data  quoted 
fit  exactly  any  given  problem.  We  urge  the  engineers  and 
architects  to  discuss  with  us  the  final,  if  not  the  lull,  details 
of  their  specific  chimney  construction  problem. 


28106 


Architect 


Two  chimneys  200'  x  8'  6"  built  in  191 


Philadelphia  General  Hospital.  Philadelphia,  Pa 


6 


Gustodis  Chimneys 


THE  Custodis  perforated  radial  brick  chimney  is  built  of  radial  blocks 
formed  to  suit  the  circular  and  radial  lines  of  each  section  of  the  chimney. 
This  permits  them  to  be  laid  with  an  even  mortar  joint  and  with  regular 
smoot h  surfaces.  In  addition  to  being  so  shaped  the  blocks  are  moulded  with 
vertical  holes  or  perforations. 


There  are  several  advantages  in  this.  The  perforations  permit  of  a  more 
thorough  burning  of  the  blocks  in  the  kilns.  This  produces  a  more  homogeneous 
block  than  could  be  obtained  were  they  solid.  Their  density  and  strength  are 
materially  increased. 

The  perforations  also  serve  to  form  a  dead 
air  space  in  the  walls  of  the  chimney  which  tends 
to  prevent  rapid  heating  and  cooling  of  the  walls 
by  conserving  the  heat  inside.  On  account  of 
their  circular  and  radial  form  tight  joints  are 
obtained.  This  with  the  air  space  due  to  perfora¬ 
tions  gives  a  maximum  conservation  of  the  heat 
inside  of  the  chimney.  (See  illustrations  showing 


radial  blocks  and  the  bonding  of  the  Custodis 


wa 


Figs.  1,  2  and  3. 


It  is  very  plain  that  with  such  shaped  blocks  a 
very  strongly  bonded  wall  can  be  built.  It  is  very 
important  not  to  make  the  perforations  excessive 
in  size.  To  retain  the  strength  of  the  block,  and 
to  prevent  the  mortar  from  filling  entirely  these 
perforations,  one  and  one-eighth  of  an  inch  square 
should  be  their  maximum  cross  section.  In 
general  the  perforations  on  the  horizontal  bed 
should  not  exceed  22  per  cent,  of  the  total  area. 

The  main  principle  of  the  perforated  radial  brick 
chimney  is  defeated  in  every  attempt  to  make  the 
perforations  larger,  in  order  to  lighten  the  material 
and  reduce  their  original  cost  and  the  cost  of 
transportation. 

In  laying  the  blocks  the  mortar  is  worked  into  the  perforations  about  one  (1) 
inch,  locking  them  together  on  the  principle  of  a  mortise  and  tenon  joint.  Each 
course  is  keyed  and  the  whole  structure  bound  together  practically  in  the  same 


Custodis  perforated  radial  brick 
const  ruction 


Georgia  School  of  Technology 
Atlanta,  Ga. 

206'6"x8'0".  Built  in  191' 


Atlanta  Water  Works 
Atlanta,  Ga. 

175'  0"x  8'  6".  Built  in  1920 


Richmond  Terminal  Railway 
Richmond,  Va. 

110'  0"  x  5'  0".  Built  in  1917 


/  f  I 


8 


manner  that  steal  dowels  of 
a  light-house  hind  the  several 
courses  of  stone  from  its 
foundation  to  its  top.  I  his 
produces  the  strongest  bonded 
wall  known  to  brick  construc- 
t  ion. 

It  will  be  noted  that  the 
horizontal  bed  joints  and 
the  cross  joints  are  not  de¬ 
pendent  alone  on  I  he  adhesion 
of  the  mortar  to  a  flat  surface. 
The  blocks  are  corrugated  on 
their  sides  in  addition  to  being 
I  >er f orated  ver  tica lly . 


Fig. 


Details  of  bonding  and  jointing  of  CUSTODIS 
perforated  radial  brick  construction 


The  Custodis  Company  gives  skilled  supervision  to  the  manufacture  of  its 
blocks.  Only  the  proper  mixtures  of  clays  are  used.  None  of  the  common  clays 
or  shale  are  used  in  Custodis  blocks.  Instead  they  are  manufactured  exclusively 
from  clays  that  are  high  in  alumina  and  high  in  silica,  giving  them  not  only  high 
refractory  powers  but  high  crushing  strength.  They  are  burned  at  a  temperature 
averaging  2000°  F.  and  have  a  maximum  crushing  strength  varying  from  1000 
pounds  per  square  inch  to  6000  pounds  per  square  inch. 


Fig.  3 

CUSTODIS  perforated  radial  chimney  blocks 


Idle  illustration  on  this  page  shows  five  (5)  different  lengths  of  blocks.  (Fig.  3.) 
All  blocks  have  the  stunt*  dimensions  on  the  face  —  namely,  approximate!) 
61  2 x Ty§  inches.  The  lengths  of  the  blocks  vary  in  order  to  make  possible  the 
breaking  of  the  joints  horizontally  and  vertically  in  the  walls.  The  combination 
of  bonds  with  this  type  of  block  admits  of  a  somewhat  lighter  wall  and  a  lighter 
chimney.  This  not  only  reduces  the  cost  of  the  foundation,  but  also  produces 
a  structure  superior  to,  but  less  costly,  than  the  common  brick  chimney  where, 
on  account  of  the  uncertainty  of  the  material  in  common  bricks,  it  is  general 
practice  to  line  a  common  brick  chimney  to  the  top. 

On  account  of  the  high  refractory  powers  of  the  blocks  to  resist  heat,  it  is 
feasible  to  eliminate  the  long  protective  lining  which  is  coninionh  used  in  the 
ordinary  common  brick  chimney. 


10 


W  ith  the  selected  clays  used  and  the  material  burned  to  a  temperature  of  at 
least  2000°  F.,  a  Customs  block  is  produced,  which  is  low  in  percentage  of 
absorption  of  moisture,  but  high  in  crushing  strength  and  refractory  powers, 
acid-proof  and  of  maximum  density. 

The  all  important  thing  in  the  manufacture  of  radial  blocks  for  chimney  use 
is  to  mix  different  and  suitable  clays  in  the  right  proportion  and  burn  I  hem  properly. 
This  knowledge  comes  only  through  study  and  long  experience. 

The  Customs  Company  ships  from  twelve  (12)  brick  yards  in  the  United 
States  and  Canada.  They  are  so  geographically  located  that  we  can  reach  almost 
any  part  of  the  country  without  excessive  freight  rates. 

The  building  of  a  chimney  requires  not  only  that  the  work  shall  be  of  the 
best,  but  that  it  shall  be  done  under  exacting  conditions  and  at  altitudes  to  which 
ordinary  masons  are  not  accustomed.  This  is  a  special  line  of  work  requiring 
trained  chimney  foremen  and  workmen  who  are  so  employed  constantly.  We 
employ  continually  numbers  of  these  men  in  organized  and  eflicient  crews. 

It  is  only  by  such  a  system,  accompanied  by  careful  and  frequent  inspections 
which  we  maintain,  that  uniform  perfect  work  in  this  line  can  be  done. 

Chapter  I 

STANDARD  TYPES 

The  application  of  the  Customs  Radial  Brick  Chimney  to  almost  every 
possible  condition  where  a  chimney  is  required  naturally  calls  for  various  and 
numerous  types  as  illustrated  in  the  following  pages. 

“A.”  FACTORY  CHIMNEY 

There  is  the  ordinary  factory  chimney  for  steam  boilers  i“or  manufacturing 
plants,  power  houses,  etc. 

In  this  case  the  chimney  is  built  for  the  express  purpose  to  produce  an  adequate 
draft  to  carry  away  a  given  volume  of  gas  at  a  requisite  velocity  that  the  boilers 
may  produce  their  maximum  economical  steam  efficiency. 

These  chimneys  are  designed  to  w  ithstand  temperatures  ranging  from  300°  F., 
w  hen  economizers  are  used,  up  to  600°  or  800°  F.,  and  are  for  boiler  purposes  alone. 
They  usually  lack  decoration  or  ornamental  design.  Their  diameter  and  height 
are  determined  solely  by  the  amount  of  cubic  feet  of  gases  they  must  handle  in  a 
given  time  to  produce  a  draft  sufficient  for  the  proper  economical  and  thorough 
burning  of  the  kind  of  coal  used.  The  lining  in  this  type  of  chimney  is  usually 
j  short  and  is  dependent,  of  course,  upon  the  internal  temperatures  expected.  It  is 

!  generally  not  more  than  one-sixth  (Veth)  the  height  of  the  chimney. 

The  chimney  can  be  built  either  of  an  all  round  column  construction  for  its 
full  height,  or  in  cases  where  the  chimney  is  connected  with  the  building  wall,  the 
lower  portion  may  be  built  of  common  brick  or  of  a  brick  to  match  that  which  is 
used  in  the  walls  of  the  power  house.  (See  detail  designs  of  the  two  types,  pages  12 
and  13.  Figures  1  and  5.  also  illustrations.) 


li 


Arlington  Mills 
Lawrence,  Mass. 
300'  0"  x  19'  O'' 

Built  in  1917 


Bush  Terminal  Co. 
Brooklyn.  N.  A . 

Two  chimneys — 200'  0"x 
12'  0"  built  in  1907  and 
275'  0"xl3'  0"  built  in  1921 


All  round  column 


12 


University  of  Washington 
Seattle,  Wash. 

200'  0"  x  10'  0" 

Built  in  1921 


Metropolitan  Edison  Co.,  Reading,  Pa. 
Four  chimneys  like  the  above  two 
Built  in  1909,  1922  and  1923 


Design  of  chimney 
Octagon  base 


11 


•‘B.”  DESK i  N S  F( )R  OFFICE  B UI LD 1 XGSJ  K )  PELS,  ETC. 

The  Ci  stodis  Kadial  Brick  Chimney  is  particular!) 
adapted  for  use  in  the  modern  office  building'. 

These  buildings  in  recent  years  reach  the  height  of  twenty 
or  more  stories.  In  the  past  steel  stacks  have  been  used, 
either  running  through  the  floors  or  banded  to  the  outside 
walls.  The  steel  stacks  radiate  heat  to  the  offices  when  the 
stack  is  entirely  within  the  building.  When  they  run  up  the 
outside  walls  they  are  often  adjacent  to  windows  where  their 
heat  is  objectionable.  Furthermore,  continual  painting  is 
necessary  for  their  maintenance  and  preservation. 

When  they  run  up  through  the  building  in  a  fireproof 
shaft  they  are  often  inaccessible  to  inspection  and  painting. 

The  substitution  of  a  CuStodis  Radial  Brick  Chimney 
in  these  cases  eliminates  all  these  objections.  They  take  up 
little  or  no  extra  space.  No  heat  is  radiated  from  them  and  when 
once  in  place  require  no  inspection,  painting  or  maintenance. 

Among  the  many  excellent  examples  of  this  type  are  the 
Custodis  Chimneys  in  the  Hotel  Commodore  and  110  Wil¬ 
liam  Street  Building  in  New:  York  City.  The  design  of  the 
latter  is  shown.  (Fig.  6.)  This  chimney  is  built  in  a  fire¬ 
proof  shaft  running  up  through  22  stories.  Note  that  there 
is  no  connection  between  it  and  the  floor  beams  of  the  building, 
the  w  alls  being  carried  to  within  approximately  inch  of  the 
steel  work.  The  chimney  stands  free  on  its  own  foundation. 
A  small  portion  extends  above  the  roof,  just  enough  to  clear 
the  pent  house.  This  portion  only  is  exposed  to  wind  pres¬ 
sure,  so  compression  is  the  one  stress  of  consideration  in  the 
structure.  This  admits  of  thin  walls  and  very  small  spread. 
The  chimney  is  plumb  throughout,  310'  0"  high  and  F  0" 
inside  diameter  at  the  top. 

In  buildings  of  less  height,  the  portion  of  the  chimney 
entirely  within  the  building  may  be  plumb  as  above  described, 
and  that  part  extending  above  the  roof,  if  of  considerable 
height,  may  be  given  a  taper  for  stability  against  wind  forces. 

The  form  may  not  necessarily  be  circular.  Many  have 
been  built  elliptical  or  oval  in  section  according  to  the  shape 
of  the  space  or  shaft  allotted  for  the  chimney. 

In  some  instances  it  is  more  practical  to  carry  the 
chimney  up  against  the  outside  walls,  close  to  the  building. 
The  plumb  portion  is  banded  with  steel  bands  every  23  or  30 
feet  and  fastened  to  the  building  wall  by  means  of  lugs.  (See 
illustration,  page  16,  Fig.  7.) 


Fig.  6 

Chimney,  No.  110  William 
Street  Bldg.,  New  York — 
310'  high;  1'  0"  inside  diam¬ 
eter  at  the  top.  Running  up 
through  22  floors.  It  is 
plumb  throughout 


15 


16 


Another  special  type  applicable  to  hotels  is  shown  in  Figure  9.  Here  the 
chimney  is  divided  into  several  compartments  by  means  of  interior  walls,  the  main 
compartment  taking  the  boiler  gases,  the  others  used  for  taking  off  the  fumes 
from  the  kitchen,  ventilating  the  dining  room  and  carrying  off  the  gases  from  a 
small  incinerator. 

The  Customs  Company  designed  and  built  several  chimneys  for  the 
Pennsylvania  R.  R.  Company  with  partition  walls  running  to  the  top.  These 
were  in  connection  with  round  houses  and  boilers.  One  compartment  took  the 
hot  gases  from  a  boiler  plant  while  the  other  carried  off  the  cooler  smoke  from 
locomotives  in  the  round  house.  (Fig.  8.) 

In  designs  of  this  character  it  is  important  not  to  bond  the  partitions  into  the 
chimney  walls,  for  their  expansion  is  likely  to  crack  the  chimney  walls. 

"The  above  are  but  a  few  of  the  designs  showing  the  almost  universal  adap¬ 
tability  of  the  Customs  Chimney  to  meet  almost  every  special  case. 

“C.”  CHIMNEYS  WITH  ARCHITECTURAL  TREATMENT 

In  connection  with  Museums,  Libraries,  Art  Galleries,  Memorials,  Public 
Buildings,  Institutions,  Colleges,  Universities,  etc.,  architects  often  require  the 
chimney  to  carry  out  in  form  and  appearance  a  particular  style  or  period  of  archi¬ 
tecture.  They  wish  to  depart  from  the  plain  shaft  with  its  straight  lines  and 
commercial  aspect.  The  Customs  Company  has  many  times  been  called  upon 
to  assist  in  the  design  of  chimneys  whose  outer  form  adheres  to  the  style  of  archi¬ 
tecture  adapted  for  the  building. 

A  handsome  example  of  this  is  the  chimney  show  n  on  page  18,  built  for  the 
Rice  Memorial  Play  Field  at  Pelham  Bay-  Park,  New  ork. 

It  is  in  the  form  of  a  fluted  memorial  column,  surmounted  by  a  terra  cotta 
urn.  The  shaft  is  after  the  Greek  columns  of  the  Parthenon  of  Athens,  period 
about  fifth  century,  R.  C.  Within  the  stone  design  of  the  column  is  a  Customs 
Chimney  serving  steam  boilers.  Some  other  examples  are  the  chimneys  built 
for  the  Betsy  Head  Memorial.  Brooklyn,  N.  A.,  page  19.  Also  the  State  Capitol 
at  Olympia,  Wash.;  General  Electric  Co.:  National  Lamp  Works,  Nela  Park. 
Cleveland,  0.;  Detroit  Water  Works,  Detroit.  Mich.;  and  others  illustrated  within 
I  hese  pages. 

The  Rice  memorial  column  particularly  shows  w  hat  can  be  done  in  constructing 
a  proper  and  ellicient  chimney  within  a  shell,  whose  lines  follow  a  definite  style  of 
architecture. 


17 


Architects ,  Herts  (**  Hotter! son,  A lew  York 

Rice  Memorial  Play  Field.  Pelham  Bay  Park,  N.  Y. 

65'  x  6'  2".  Built  in  1921 

A  chimney  in  the  form  of  a  memorial  column  on  the  top  of  which  is  a  terra  cotta  urn.  The  shaft  is  after  the  Greek  Doric  Columns 
of  the  Parthenon  of  Athens.  Period  about  5th  Century  B.  C.  Within  the  stone  facing  is  a  Custodis  Chimney 


18 


Detroit  Water  Works 
Detroit.  Mich. 

Two  chimneys  150'  0"  x  12'  0" 
Built  in  1921 

An  ornate  chimney  with  ornamental 
head — stone  trimmed 


\\  ilder  df  H  hilc,  Arch  Her  l 

Washington  State  Capitol 
Olympia.  Wash. 

1  IT'  6"  x  6'  6".  Built  in  1920 
An  ornate  Custodis  chimney  faced 
with  cut  stone 


_ Herts  if  Robertson ,  I\'ew  York,  Architects 

Betsy  Head  Memorial  Playground 
Brooklyn,  N.  Y. 

88'  5"  x  1'  0".  Built  in  1915 
A  Greek  Doric  Column  built  of 
Custodis  radial  chimney  brick 
surmounted  by  a  terra 
cotta  memorial  urn 


In  a  number  of  large  power 
houses  Custodis  Chimneys  of 
considerable  size  are  built  on  the 
structural  steel  near  the  roof  line. 
This  conserves  room  in  the  station 
and  often  shortens  the  breechings 
from  boilers  to  stack,  lowering  the 
cost  of  the  latter  as  well  as  reducing 
the  friction  losses.  Notable  ex¬ 
amples  of  this  type  are  the  Cus¬ 
todis  Chimneys  at  the  Power 
Stations  of  the  New  \ork  Central 
R.  R.  Co.  at  Port  Morris  and 
5  onkers,  New  'l  ork,  the  interboro 
Rapid  Transit  Station  at  59th  Street, 
Nev  5  ork,  the  Municipal  Electric 
Light  Plant.  Lansing,  Mich.,  and 
Consolidated  Gas,  Electric  Light  & 
Power  Co.,  Westport,  Md.  The 
illustration  (Fig.  10).  is  typical  and 
shows  the  foundation  on  steel. 


I'k 

Chimney  on 


Consolidated  Gas,  Electric  Light  &  Power  Co.,  Westport,  Md. 

Three  chimneys.  215'  0"  x  20'  2".  Built  in  1913,  1917  and  1918 

Chimneys  on  structural  steel  90'  from  ground 


20 


Illinois  Glass  Co.,  Bridgeton,  N.  J. 
170'  x  T  Built  in  1921 


J .  E.  U  oodwell ,  Engineer 

Moores  Park  Station 
City  of  Lansing,  Michigan 
Two  chimneys  200'  \  PI'  0"  Built  in  1923 
Chimney  on  structural  steel 


If.  L.  Doherty  df  Co.,  Engineers 

Public  Service  Co.  of 
Colorado 
Valmont,  Col. 

350'  x  16'  Built  in  1921 


1 


“D.”  HIGH  TEMPERATURE  CHIMNEYS 

"These  chimneys  are  used  in  connection  with  furnaces,  smelters,  incinerators, 
garbage  destructors,  etc.,  where,  in  addition  to  providing  draft,  they  must  stand 
high  internal  temperatures. 

As  stated  heretofore,  chimneys  used  in  connection  with  steam  boilers  where 
the  temperatures  range  between  300°  F.  anti  600°  F.  it  is  necessary  to  line  only  a 
portion  of  the  chimney.  Where  the  boilers  are  pushed  to  an  overload  of  150  or 
200  per  cent,  or  more  above  normal,  in  the  absence  of  economizers  or  other  appara¬ 
tus  that  would  lower  the  temperature  of  the  gases  before  entering  the  chimney, 
higher  stack  temperatures  may  be  expected. 

If  these  do  not  reach  over  1000°  F.  it  is  not  necessary  to  line  the  chimney 
to  the  top,  but  it  is  well  to  increase  the  length  of  lining  above  the  customary  one- 
sixth  (i/gth)  the  height.  Should  tin*  chimney  temperatures  run  over  1000°  F.  and 
up  to  1200°  F.,  it  is  good  practice  to  line  it  with  sectional  lining  of  Custodis 
Radial  Brick  for  its  lull  height.  The  lining  is  supported  on  corbels  built  out  from 
the  main  walls  at  intervals  of  approximately  20  feet  vertically,  with  an  air  space 
of  not  less  than  2  inches  between  the  lining  and  the  walls. 

For  temperatures  ranging  from  1200°  to  1500°  F.,  where  no  destructive  acids 
are  present,  we  recommend  an  independent  lining  of  Custodis  Radial  Brick 
for  the  full  height  of  the  chimney  with  an  ample  air  space  between  it  and  the  chim¬ 
ney  wall.  The  lining  should  have  no  connection  with  the  main  walls  and  be  abso¬ 
lutely  free  to  expand  at  the  top. 

It  is  advisable  to  use  mortar  composed  of  lime,  sand  and  cement  when  the 
above  or  less  temperatures  are  present.  Fire  clay  is  not  recommended,  for  the 
lime,  sand  and  cement  mortar  gives  a  stronger  bond  and  answers  the  purpose. 

If  the  internal  temperatures  expected  are  above  1500°  F.  and  up  to  2000°  F., 
an  independent  lining  of  solid  radial  lire  brick  for  the  full  height  of  the  chimney 
shall  be  employed.  In  this  case  we  recommend  that  the  solid  radial  fire  brick 
lining  be  laid  up  in  lire  clay  with  a  small  quantity  of  cement.  Internal  steel  bands 
should  be  built  into  the  walls  of  the  chimney  at  every  change  of  section  to  assist 
in  taking  up  the  thermal  strains.  (See  Fig.  11.) 

The  internal  ladder  generally  used  should  be  eliminated  in  chimneys  subjected 
to  these  high  temperatures,  for  the  reason  that  if  the  ladder  step  irons  are  built 
through  the  lining  and  into  the  main  walls,  when  the  lining  expands  they  are 
liable  to  crack  both  the  lining  and  the  chimney. 

Chimneys  subjected  to  temperatures  over  2000°  F.  should  be  constructed 
with  an  independent  solid  radial  fire  brick  lining  laid  in  fire  clay  mortar  as 
described  above. 

In  addition  to  the  independent  lining  an  additional  lining  of  the  very  best 
obtainable  high  refractory  lire  brick  should  be  constructed  in  the  lower  portion 
inside  the  independent  lining,  but  not  bonded  to  it.  Under  continued  temperatures 
over  2000°  F.  the  lire  brick  in  the  lower  portion,  particularly  in  the  vicinity  of 


99 


The  Don  Incinerator 
Toronto,  Ont..  Canada 
175'  0"  x  7'  6".  Built  in  1916 
This  chimney  subjected  to 
temperatures 


Chimney  for  high  tem¬ 
peratures  up  to  2000°  F. 
Independent  lining  of 
solid  lire  brick 


Section  A  \  Fig.  12 

of  F  ig-  12  Chimney  for  temperatures  over 

2000°  F.  t\  ith  independent  solid 
radial  fire  brick  lining  to  top  and 
removable  fire  brick  lining  in  lower 
portion 


25 


o'-  o' _  V _ 14-'- 


the  flue,  wil  1  in  time  burn  out.  This  necessitates  the  removal  and  replacement  of 
this  removable  portion.  The  fact  that  it  is  not  bonded  to  the  main  lining  makes 
its  removal  and  renewal  possible  without  disturbing  the  main  lining. 

We  would  further  recommend  building  on  the  outside  of  the  chimney  steel 
bands  at  intervals  of  between  8  and  10  feet  vertically.  (See  drawing  illustrating 
this  type,  Fig.  12.) 

RESISTANCE  TO  EARTI [QUAKES,  EXPLOSIONS  AND  SHOCK 

It  has  been  demonstrated  many  times  that  the  Custodis  radial  brick  chim¬ 
neys  resist  successful! \  such  unusual  shocks  as  concussions  due  to  explosions  and 
earthquakes,  as  well  as  shocks  from  heavy  rock  blasting,  and  vibrations  from 
hydraulic  or  steam  hammers. 

Although  there  were  a  number  of  these  chimneys  in  Ihe  area  covered  by  the 
San  Francisco  earthquake,  they  were  not  damaged. 

The  well-remembered  explosion  of  TAT  in  the  Harbor  of  Halifax  in  December, 
1017.  during  the  World  War,  wrecked  many  structures  and  buildings  in  Halifax 
and  Dartmouth,  N.  S.  On  the  day  of  the  explosion  the  Custodis  Company 
had  practically  finished  six  radial  brick  chimneys  for  The  Imperial  Oil  Company 
at  Dartmouth.  These  chimneys  were  practically  green.  Structures  and  buildings 
were  wrecked  all  around  them,  but  the  chimneys  themselves  were  not  injured  in  the 
least.  They  stood  within  a  mile  of  the  explosion.  There  were  some  fifteen  older 
Custodis  chimneys  within  this  area  and  none  of  them  were  injured  in  the 
slightest  degree. 

The  Black  Tom  explosion  during  the  W  orld  W  ar,  at  Communipaw,  N.  J.,  also 
wrecked  structures  and  buildings  in  that  vicinity.  In  this  area  there  were  a  large 
number  of  Custodis  chimneys.  These  chimneys  withstood  the  concussion  and 
none  of  them  were  injured  in  any  way  or  developed  defects  since. 

There  are  a  number  of  installations  of  Custodis  chimneys  in  the  vicinity 
of  quarries  where  they  are  blasting  continually.  These  chimneys  have  not 
been  affected. 

Many  Custodis  radial  brick  chimneys  stood  within  the  area  covered  by 
the  tropical  cyclone  and  hurricane  of  September,  1915,  in  southern  Louisiana  and 
Mississippi.  Their  heights  ranged  from  165  feet  to  200  feet.  The  L  nited  States 
Weather  Bureau  reports  an  extreme  wind  velocity  in  certain  areas  of  over  130 
miles  per  hour,  and  further  say  that  pulsating  gusts  of  a  few  seconds'  duration  were 
at  times  undoubtedly  much  greater  than  the  extreme  velocity  of  130  miles  per  hour. 
The  Custodis  chimneys,  in  this  area,  were  in  no  way  affected  by  this  extreme 
and  practically  unprecedented  wind. 

These  incidents  are  ample  proof  that  the  factors  used  by  the  engineers  of  the 
Custodis  Company  in  designing  their  chimneys  are  conservative  and  safe,  and, 
furthermore,  that  the  design  of  the  whole  structure  in  taper,  spread,  wall  thickness 
and  weight  are  of  the  best  that  long  experience  and  good  judgment  can  produce. 

:■  - . 


24 


Chicago  &  Northwestern  Railway  Co.,  Chicago,  111. 

203'  0"  x  12'  0".  Built,  in  1916 

On  March  19th,  1921,  the  grain  elevator  in  t lie  Yards  of  the  C.  &  N.  \\  . 
Railway  blew  up. 

The  concrete  elevator,  elevator  buildings,  power  house,  loading  and 
welfare  buildings  were  completely  wrecked. 

The  Custodis  radial  brick  chimney  adjacent  to  the  elevator  was  the 
only  structure  that  withstood  the  shock  and  remained  intact. 

A  demons! ration  of  the  stability,  durability  and  strength  of  the  modern 
Custodis  radial  brick  chimney. 


St.  Paul  &  Tacoma  Lumber  Co.,  Tacoma,  Wash. 
Two  chimneys  150'  0"  x  9'  0".  Built  in  1920 
Replacing  two  steel  stacks  which 
have  since  been  removed 


American  Woolen  Co. 
Shawsheen  \  illage 
Andover,  Mass. 
250'  0"  x  12' 

Built  in  1921 


U.  S.  Public  Health 
Hospital 

W  alla  Walla,  Wash. 
127'  0"  x  4'  6" 
Built  in  1922 


Edison  Lamp  Works 
Harrison,  N.  J. 

1 75'  0"  x  7'  6" 
Built  in  1918 

Name  built  into  chimney 
with  while  enamel  brick. 
Each  letter  approximately 
4'  7"  high. 


NAMES,  LETTERS,  DECORATIONS 

Many  firms  take  advantage  of  their  chimney  to  use  it  as  a  means  of  adver¬ 
tisement  by  placing  the  firm  name  or  initials  in  a  vertical  position  on  the  column. 

Some  have  a  taste  for  a  decorative  pattern  at  the  top.  Illustrations  of  the 
use  of  names,  letters  and  decorations  are  shown  on  pages  27  and  28. 

These  are  formed  by  building  into  the  structure  radial  chimney  blocks  the 
color  of  which  is  in  marked  contrast  with  the  body  color  of  the  shaft. 

On  a  chimney  buff  in  color,  blocks  of  dead  black  are  usually  used.  During 
their  manufacture  a  black  preparation  is  put  on  the  faces  of  the  blocks  when 
green.  It  is  then  burned  permanently  into  them  as  they  are  fired  in  the  brick 
kilns.  This  makes  the  black  absolutely  permanent,  as  well  as  weather  and  heat 
proof. 

If  the  chimney  shaft  be  red  then  blocks  of  light  buff  color  may  be  used.  They 
make  a  striking  contrast  with  the  dark  red  background. 

A  very  handsome  and  effective  appearance  is  obtained  by  forming  the  letters 
with  glazed  enamel  brick  of  different  colors — such  as  white  enamel  on  a  red  chim¬ 
ney  and  dark  brown,  dark  maroon  or  deep  dark  blue  on  a  buff  chimney. 

The  glazed  surface  of  the  enamel  brick  is  not  easily  discolored.  What  little 
soot  does  gather  on  them  is  quickly  washed  off  by  the  rain,  and  the  surface  is 
again  bright  and  clear. 

The  size  of  the  letters  varies  with  the  size  of  the  chimney.  The  larger  the 
chimney,  the  larger  the  letter  which  can  be  used  with  effect.  They  range  in 
height  from  two  feet  eleven  inches  to  seven  feet  or  more. 

Elevated  as  the  letters  are  on  a  tall  chimney,  they  attract  marked  atten¬ 
tion.  Compared  with  the  same  size  letter  put  on  by  a  sign  painter  the  cost  is  not 
large.  Furthermore,  paint  in  time  will  wear  off.  while  the  built-in  letters  are 
absolutely  permanent. 

Were  the  sides  of  the  letters  made  straight  with  separate  bricks  or  blocks,  they 
would  not  break  joints  and  the  strong  bond  of  the  Custodis  chimney  would 
be  destroyed.  For  that  reason  the  letters  are  worked  out  in  broken  lines. 

PROTECTIVE  AND  DECORATIVE  HEADS 

The  standard  head  for  factory  chimneys  is  shown  in  Fig.  13.  The  tops  of 
acidproof  chimneys  are  protected  w  ith  a  cap  made  of  material  not  affected  by  the 
particular  acid  the  chimney  handles,  as  show  n  in  Fig.  15.  Ornamental  heads  are 
exemplified  in  Figs.  16  and  17  and  can  be  furnished  at  slight  additional  cost. 
Many  different  styles  of  heads  may  be  designed  to  suit  the  architecture  of  the 
building  or  the  particular  taste  of  the  owner  or  architect. 


26 


Vancouver  Lumber  Co.  17.V'  x  9" 
Vancouver  B.  C. 

Built  in  1922 

\\  bite  enamel  brick  letters  each  o'  5"  high 
Length  of  name  102  feet 


The  Buda (  io., 
Harvey,  Ill. 
200'  0"  x  9'  0" 
Built  in  1917 


Northwest  Paper  Co.,  Cloquet,  Minn. 
Two  chimneys 
175'  x  9'  0".  Built  in  1914 
250'  x  14'  0".  Built  in  1922 


- i  f -  r/ 


Atlanta  Terra  Cotta  Co. 
Perth  Amboy,  N.  J. 
110'  0"  x  5'  6" 


White  Provision  Co. 
Atlanta,  Ga. 


Built  in  1922.  Light  BUFF  col¬ 
umn  with  deep  BLUE  enamel 
letters  and  decoration 


125'  0"  x  7'  O'' 

Built  in  1923.  RED  column  with 
WHITE  enamel  brick  letters. 
Note  cored  concrete  sub-base  and 
foundation 


Patterson  Realty  Co. 
Nashua,  N.  H. 

70'  0"  x  3'  0" 


s 

T 

R 

A 

T 

F 

O 

R 

D 


O 

A 

K 

U 

M 


4h 


Stratford-Oakum  Co. 
Jersey  City,  N.  J. 
125'  0"  x  4'  0" 


Built  in  1922.  Light  BUFF  col¬ 
umn  with  BLACK  letters.  Note 
cored  concrete  sub-base  and  foun¬ 
dation 


Built  in  1919.  Dark  RED  column 
with  WHITE  enamel  brick  letters 


28 


Fig.  13 

Slandaril  head 


Head  with  concrete 
capping 


Fig.  15 

Mead  of  chimney  with 
lining  to  top  showing 
lend  cap 


FLUE  OPENINGS 

For  structural  reasons  avc  recommend  a  line  opening  rectangular  in  shape, 
and  of  an  area  equal  to  the  total  area  at  the  top  of  the  chimney  plus  ten  per  cent 
(10%).  This  will  develop  the  full  working  horse-power  of  the  chimney. 


Fig.  20 
Section 
through 
t  ypical 
flue  opening 


Fig.  21 

Section  through  all-round 
chimney  located  on  side 
of  building 


Fig.  24 

Section  through  octagon  base  chimney 
located  in  corner  of  building 


Fig.  22 

Section  through  square 
base  chimney  located  in 
corner  of  building 


Fig.  25 

Section  through  chimney 
showing  baffle  w  all 


Fig.  23 

Section  through  square  base  chimne; 
located  on  side  of  building 


Fig.  26 

Elevation  of  baffle  wall 


Reinforcing  piers  are  built  out  on  each  side  of  the  opening  from  the  main 
walls.  The  faces  of  the  piers  are  a  plain  surface  vertical  to  the  ground.  The 
masonry  above  the  opening  is  supported  by  heavy  I-beams.  It  is  further  rein¬ 
forced  top  and  bottom  by  means  of  steel  bands  built  into  the  chimney  walls.  See 
section  of  Hue  opening,  page  29.  Fig.  20. 

To  maintain  a  safe  moment  of  stability,  the  width  of  Hue  opening  is  limited 
for  round  chimneys  approximately  to  one-third  the  width  of  the  chimney  at  the 
point  where  the  Hues  enter;  for  octagon,  seven-sixteenths;  for  square,  one-half. 

We  recommend  certain  widths  and  heights  for  dilferent  inside  top  diameters 
of  chimneys.  These  sizes  are  given  in  table  1.  page  30,  and  it  is  well  not  to  exceed 
them.  The  sizes  given  will  develop  the  full  working  horse-power  of  the  chimney. 

Where  the  chimney  is  designed  for  two  line  openings  on  the  same  elevation 
and  directly  opposite,  a  bailie  wall  is  necessary  to  prevent  interference  of  the  two 
gas  streams  and  to  assist  in  their  upward  trend.  See  page  29,  Figs.  25  and  26. 
The  bailie  wall  should  be  set  at  an  angle  of  15  degrees  with  the  entering  lines.  It 
may  start  two  feet  below  the  openings  and  extend  three  or  four  feet  above  them. 

When  not  resting  on  the  foundation  the  bailie  wall  may  be  supported  on 
I-beams  and  built  against  the  lining,  but  not  bonded  to  it  nor  to  the  main  walls. 

Table  2,  below,  gives  the  proper  sizes  of  two  line  openings  entering  a 
chimney  where  the  Hue  openings  are  of  equal  capacity. 


TABLE  i 

SINGLE  FLUE  SHOWING  MAXIMUM  WIDTHS  OF  FLUES  AND  SIZES  OF  FLUE  OPENINGS  FOR  STACKS  OF 

VARIOUS  DIAMETERS 


Diara. 

FLUE  DIMENSIONS 

Diam. 

FLUE  DIMENSIONS 

ol 

ol 

Chimney 

Square  Rase 

Octagon  Base 

Round  Col. 

Chimney 

Square  Rase 

Octagon  Base 

Round  Col. 

2 '-6" 

2'-0'x  2'-  9' 

2  -0’x  2'-  9' 

2 '-O'x  2'-  9' 

1  1  -6' 

8'-  6'x  13'-  5' 

8 '-0'x  14'-  6' 

7'-3"xl5'-  6' 

3-0' 

2'-6'x  3'-  2' 

2'-6'x  3'-  2' 

2-6'x  3'-  2' 

12-0' 

8'-  6'x  14  -  7' 

8 '-0'x  1 5'-  7' 

7'-6'xl6  -  0' 

3-6' 

3'-0"x  3'-  6’ 

3 '-O'x  3  -  6' 

2'-9'x  3 -nr 

12-6' 

8 '- 1 1 "  x  1 5 '-  5  ' 

8 '-4'x  16'-  3' 

7'-9'xl7'-  5' 

4-0' 

3-3'x  4'-  3' 

3  -3'x  4  -  3' 

3 '-O'x  l'-  7' 

13-0' 

9'-  I'xl5'-10” 

8'-8'x  1  6'-l  1 " 

8'-0'x  18'-  3' 

4 '-6" 

3'-6'x  5'-  2 ' 

3'-6'x  5'-  2' 

3-3’x  5'-  6' 

13-6' 

9'-  9'x  16'-  3' 

9'-0'x  17'-  6' 

8'-3'xl9'-  1' 

5-0" 

4 '-0'x  5'-  5’ 

4 '-O'x  5'-  5’ 

3'-6’x  6'-  2' 

14-0' 

10'-  2'xl6-  8' 

9 '-4'x  1 8'-  2" 

8'-6'x  19'-1 1 ' 

5  '-6 " 

4 '-6'x  5'-l0" 

4 '-3'x  6'-  O' 

4 '-O'x  6-7' 

14-6' 

10'-  7'x  1 7'-  2' 

9'-8"x  18-10' 

8'-9'x20'-  9" 

6 '-O’ 

5'-0’x  6'-  3’ 

4'-6'x  7'-  0’ 

4  '-3’x  7'-  5' 

15-0' 

11-  0'xl7'-  8" 

lO'-O'x  1 9'-  6' 

9'-0'x21 '-  7" 

6 '-6" 

5'-6’x  6'-  8’ 

4'-9'x  7'-  9' 

4  '-7'x  8'-  2’ 

15-6' 

1 1 '-  5'x  18'-  2' 

10'-4'x20-  2' 

9'-3'x22'-  5' 

7 '-0’ 

5'-9'x  7'-  5' 

5-3'x  8'-  6' 

5  -O'x  8'-  6' 

16-0' 

1  1  '- 1 0'x  1 8'-  8' 

1 0'-8'x20'-10' 

9'-6"x23'-  3' 

7  -6" 

6 -O'x  8'-  1 

5 -6'x  8  -10' 

5  -3'x  9  -  4' 

16-6' 

12  -  3'x  19'-  2' 

1  l'-0'x21'-  5' 

9'-9'x24'-  1' 

8 '-0’ 

6 '-6'x  8'-  6' 

5  -9'x  9'-  8' 

5 '-6'x  10'-  O' 

1  7'-0' 

12'-  8'x  19'-  9’ 

ll-4'x22'-  1 

1 0'-0'x25'-  0' 

8 '-6' 

7  '-0*x  9  -  0' 

6  -3'xlO'-  O' 

5'-9'xl0'-  9' 

17-6' 

13'-  1  ”x20'-  3' 

1  l'-8'x22'-  9' 

1  0'-3"x25'-10' 

9'-0" 

7'-6'x  9'-  3* 

6 -6'x  1  O'-  9’ 

6-'0'xll'-  8' 

18-0' 

13'-  6'x20'-  9' 

12'-0'x23'-  4' 

10'-6"x26'-  8' 

7'-9’xl0'-  O' 

6'-9'xll'-  6" 

6'-3'x  12'-  6' 

18-6' 

1 3  -1 1  "x2 1  -  3' 

12'-4'x24'-  O' 

10'-9'x27'-  6' 

lO'-O" 

8 -Cxi O'-  9’ 

7'-0'xl2'-  4" 

6 -6'x  13'-  3' 

19'-0' 

1  1-  4'x21-  9' 

12'-8'x24'-  8" 

1  l'-0"x28'-  5" 

10 '-6" 

8  -6'xll'-  3' 

7'-0'x  13'-  7" 

6-9'xll-  r 

19-6' 

1  1  -  9"x22'-  3' 

1 3 '-O'x 25'-  4' 

1  1  '-3'x29'-  3' 

1 L  -0" 

8'-6"xl2'-  3' 

7'-6'xl3'-10' 

7'-0'xl4'-10' 

20'-0" 

15'-  2"x22'-  9” 

13'-4'x26'-  0' 

1  l'-6'x30'-  1' 

TABLE  2 

TWO  FLUES  OF  EOUAL  SIZE.  EACH  FOR  HALF  CAPACITY,  SHOW  ING  MAXIMUM  W  IDTHS  OF  FLUES  AND  SIZES 

OF  FLUE  OPENINGS  FOR  STACKS  OF  VARIOUS  DIAMETERS 


Diam. 

FLUE  DIMENSIONS 

Diam. 

FLUE  DIMENSIONS 

ol 

ol 

Chimney 

Square  Rase 

Octagon  Rase 

Round  Col. 

Chimney 

Square  Rase 

Octagon  Base 

Round  Col. 

2 '-6' 

U-  9"x2'-  0’ 

1-  9'x2'-  0' 

1'-  9'x2'-  0' 

11-6' 

7'-  2'x  8'-  0' 

6'-  3'x  9'-  3’ 

5'-10'xl0'-  0" 

3 '-0" 

2'-  0'x2'-  3' 

2'-  0'x2'-  3' 

2'-  0'x2  -  3’ 

12-0' 

7'-  6'x  8'-  4' 

6'-  6'x  9'-  8' 

6  -  O'x  10'-  5' 

3  '-6" 

2'-  3"x2'-  9’ 

2'-  3'x2'-  9' 

2'-  3'x2'-  9' 

12'-6* 

7'-  7'x  9'-  0' 

6'-  7'x  10'-  4' 

6'-  2'x  11'-  1' 

4'-0" 

2'-  6'x3'-  2' 

2'-  6"x3'-  2' 

2'-  6'x3'-  2' 

13 '-0' 

7'-  8'x  9  -  7' 

6'-  8'x  11-  0' 

6'-  3'x  11'-  9' 

4 '-6' 

2'-  9”x3'-  6" 

2'-  9'x3'-  6' 

2'-  8'x3'-  7' 

13-6' 

7'-  9'xl0'-  2' 

6'-10'xl  1 '-  8" 

6'-  4'xl2'-  7' 

5'-0" 

3  -  1  'x3 '-  9' 

3  -  l’x3-  9' 

2'-l  1  'x4'-  O' 

14 '-0' 

7  -1  1'xlO  -  9' 

7'-  O'x  12'-  3' 

6'-  5'xl3'-  2' 

5 '-6" 

3’-  4’x3'-  0' 

3'-  4’x4'-  0” 

3'-  l'x4'-  6" 

14'-6' 

8'-  l'xll-  4' 

7'-  2'xl2'-  9' 

6'-  7'x  13'-  9' 

6 '-O’ 

3'-  7"x4'-  6" 

3'-  7'x4'-  6' 

3'-  3'x5'-  O' 

15'-0' 

8'-  3'xir-Il' 

7'-  5'x  13'-  4' 

6'-10’xl4'-  4' 

6 '-6" 

3'-ll"x4'-10' 

3'-10’x4'-ll' 

3'-  6'x5'-  5' 

1 5  '-6 ' 

8  -  5'x  12'-  6' 

7'-  7'x  1 3'-10’ 

7'-  0'xl4'-ll' 

7'-0' 

4'-  2"x5'-  2' 

4'-  0’x5'-  5' 

3'-  9'x5'-10' 

16 '-O' 

8'-  6'x  1 3'-  1 " 

7'-  9'xl4'-  4' 

7'-  2'xl5'-  6' 

7 '-6" 

4'-  6"x5'-  6" 

4'-  3'x5'-10" 

4'-  0'x6'-  2' 

16-6' 

8'-  8'xl3'-  8' 

7'-ll'xl4'-ll* 

7'-  4'x  16'-  1' 

8 '-O’ 

4'-10"x5'-10' 

4'-  6'x6'-  3' 

4'-  3'x6'-  8' 

17-0' 

8'-10'xl4'-  3’ 

8'-  l'xl5'-  5' 

T-  6'xl6'-  8’ 

8-6' 

5'-  l"x6'-  2' 

4'-  9'x6'-  8' 

4'-  6'x7'-  1' 

1 7  '-6  ’ 

9  -  0'xl4'-10' 

8  -  4’x  16'-  0' 

7'-  8'xl7'-  3' 

9'-0' 

5'-  5 "x6 '-  6’ 

5'-  O'x 7'-  1" 

4'-  9'x7'-  7' 

18-0' 

9  -  2'x  15'-  5' 

8'-  6'xl6'-  6' 

7'-ll'xl7'-10' 

9-6' 

5'-  9'x6'-10" 

5'-  3'x7'-  6' 

5'-  0'x8'-  0' 

18 '-6' 

9  -  4'xl5'-Il' 

8  -  8'xl7'-  1' 

8'-  l'xl8  -  5' 

10'-0' 

6  -  l"x7'-  2" 

5'-  6"x8'-  0" 

5'-  3"x8'-  6' 

19-0' 

9  -  9'xl6'-  2" 

9'-  O'x  17'-  5' 

8'-  3'x  19  -  0' 

10 '-6' 

6'-  5"x7'-  5' 

5'-  9"x8'-  5' 

5'-  6'x9 '-  0' 

19-6' 

10'-  2"xl6'-  4' 

9-  4'xl7'-  9" 

8'-  5'xl9'-  7' 

11 '-0* 

6'-10"x7'-  9" 

6'-  0'x8'-l O' 

5'-  8"x9'-  6' 

20 '-0' 

10'-  6'xl6'-  6' 

9'-  7'x  18'-  1' 

8'-  7'x20'-  2' 

30 


Imperial  W  ire  &  Cable  Co  . 
Montreal.  P.  0. 
225'xlO" 

Built  in  1910 


General  Electric  Co.  (National  Lamp  W  orks) 
Nela  Park  (Cleveland 

Two  chimneys  86'  1"  x  7'  0".  Built  in  191 1  and  162(1 
Note  the  entasis  in  the  round  shaft 


J. 


Delawanna.  N 
165'  0" x  7' 

Built  in  1919 
Top  decoration  built 
of  white  enamel  brick 


31 


II’  one  Hue  opening  serves  less  boiler  horse-power  than  the  other,  the  sizes 
should  be  proportioned  accordingly. 

Within  limits,  a  chimney  may  be  economically  and  safely  built  sufficiently 
large  to  take  care  of  future  additional  boilers.  In  this  case  we  recommend  that  the 
Hue  opening  in  t lie  chimney  be  built  t lie  full  size.  The  breeching,  for  a  few  feet 
from  the  chimney,  is  made  the  full  size  of  the  opening,  then  properly  reduced  in 
section  to  take  the  gases  of  the  lirst  boilers  installed.  In  this  manner,  when 
additional  boilers  are  added,  they  can  be  connected  to  the  full  size  breeching  at 
the  chimney  without  disturbing  the  masonry  in  the  chimney.  Provision  should  he 
made  in  the  breeching  for  the  future  connection  of  additional  boilers. 


University  of  Washington.  Seattle.  Wash.,  plant  shut  clown  eight  hours  while  [tutting 

new  chimney  in  service 


AN  OLD  STACK  CAN  BE  REPLACED  BY  A  NEW  CHIMNEY  WITH  A 
SHUT  DOWN  OF  ONLY  A  FEW  HOURS 

Power  plant  owners  often  have  to  face  the  problem  ol  renewing  old  stacks  or 
of  building  a  larger  chimney. 

It  is  possible,  but  not  generally  practicable,  to  build  a  masonry  chimney 
around  an  old  steel  stack  to  avoid  a  shut  down,  but  we  recommend  against  this 
procedure. 

A  ery  often  the  new  chimney  can  be  located  close  to  the  old  one.  In  that  case 
the  old  stack  can  be  kept  in  operation  until  the  new  one  is  entirely  completed 


with  Hue  opening  ready  to  be  connected  up.  With  the  new  breeching  and  con¬ 
nections  already  fabricated  and  on  the  ground,  the  old  stack  may  be  cut  out  on  a 
Saturday  or  a  holiday  and  the  new  chimney  connected  up  in  a  few  hours,  after 
which  the  old  stack  may  be  removed. 

The  Custodis  Company  has  built  new  chimneys  directly  behind  old 
chimneys,  connected  the  new  chimneys  up  by  means  of  a  breeching  directly  through 
the  old  stacks  and  put  the  new  chimneys  in  operation  directly  after  shutting  down 
the  old  ones.  See  illustration,  page  32. 

Our  Engineers  are  experts  in  all  such  difficult  and  apparently  baffling  chimney 
problems.  We  solicit  an  opportunity  to  solve  them  for  you. 

REPAIRS  TO  AND  HEIGHTENING  OF  OLD  CHIMNEYS 

In  addition  to  crews  of  expert  chimney  builders,  the  Custodis  Company 
maintains  organized  crews  of  expert  steeplejack  masons,  who  recondition  old 
chimneys,  repair  and  renew  the  heads,  repoint  the  weathered  surfaces  of  old 
structures  for  their  preservation  and  longer  life,  straighten  chimneys  that  lean 
and  repair  those  struck  by  lightning.  They  also  demolish  old  chimneys,  repair 
and  renew  lightning  rods. 

Many  old  chimneys  are  capable  of  being  heightened.  We  accomplish  this 
work,  if  necessary,  while  the  chimney  is  in  operation  without  interruption  to  the 
plant.  See  illustration,  page  34. 

Calculations  should  lie  made  to  determine  whether  or  not  the  chimney  is 
capable  of  being  heightened  without  impairing  its  stability.  The  foundation  and 
old  brick  work  should  be  examined  to  determine  whether  they  will  stand  the 
additional  weight  and  wind  stresses. 

If  such  a  proposition  is  under  consideration,  send  ns  a  plan  of  the  old  chimney 
and  our  Engineers  will  determine  how  much,  if  at  all,  the  chimney  can  safely  be 
heightened.  If  a  plan  is  not  available,  advise  us  the  cross  section,  whether  octagon, 
square  or  round,  the  height  above  the  foundation,  the  inside  diameter  at  the  top, 
the  outside  dimensions  at  the  foot  and,  as  nearly  as  possible,  the  lop  outside 
measurements,  and  also  the  wall  thickness  at  the  bottom.  This  last  may  often 
be  obtained  through  the  cleanout  door. 

NEW  OPENINGS  CUT  IN  OLD  CHIMNEYS 

It  is  often  found  necessary  to  cut  new  openings  in  a  chimney  where  changes 
or  additions  are  made  in  a  plant,  but  this  should  never  be  attempted  without  first 
obtaining  expert  advice.  The  reduction  of  cross  sectional  area  may  impair  the 
stability  of  the  chimney.  This  can  be  determined  only  by  careful  calculations. 
The  position  of  the  new  Hue  opening  w  ith  respect  to  the  old  is  an  important  factor 
in  determining  whether  or  not  it  is  safe  to  cut  the  new  flue  opening. 

Our  Engineers  are  prepared  to  make  such  calculations  for  you  and  advise  you 
not  only  as  to  the  safety,  but  as  to  the  maximum  size  opening  possible  and  its  best 
position. 


33 


If  a  second  opening  is  cut  and  the  original  opening  left  in  operation,  a  baffle 
wall  is  sometimes  a  necessity  to  prevent  the  gases  from  the  two  Hues  interfering 
with  each  other  and  impairing  the  draft.  See  page  29.  An  extension  of  the  inner 
lining  may  also  be  necessary. 


When  it  is  determined  that  such  openings  can  safely  be 
cut,  the  work  should  not  be  done  by  inexperienced  workmen. 

Our  chimney  crews  are  trained  to  safely  accomplish  such 
work  without  injury  to  the  structure.  Great  care  and  a 
certain  routine  method  are  necessary. 


Reconditioning  an  old  chim¬ 
ney.  This  can  be  done  while 
chimney  is  in  operation  if 

necessary 

Note  platforms  for 
determining  chimney 
performance 


Oregon  Agricultural 
College 
Corvallis.  Ore. 

17^'vlfl'  "R.iiH  in  1  Q93 


Showing  the  heightening  of  two  chimneys  while  the 
chimneys  are  in  operation. 


34 


Cornell  University,  Ithaca,  N.  Y. 
225'  0"  x  11'  0".  Built  in  1922 
Note  ladder,  experimental  plat¬ 
forms  and  openings  for  taking 
observations 

Henry  It.  Kent  &  Co.,  Engineers 
Rutherford ,  N.  J. 


Built  in  1905 


This  chimney  stood  in  the  area 
covered  by  the  tropical  cyclone 
and  hurricane  of  September.  1915, 
in  Southern  Louisiana  and  Missis¬ 
sippi.  It  remained  in  perfect 
condition 


Interboro  Bapid  Transit  Co. 

74th  St.  Station,  New  ^  ork 
Four  chimneys  278'  0"x  17'  0" 
Built  in  1900 

Five  others  162'xl5' — 59th  St.  Station. 
Built  in  1902 

One  162' x  20' — 59th  St.  Station 
Built  in  1923 

These  last  six  built  upon  the  structural 
steel  of  the  building 

Geo.  H.  Pegram ,  Engineer 


New  OrleansPumping Station 
New  Orleans,  La. 


35 


West  Virginia  Pulp  &  Paper  Co., 
Covington,  Va. 

250'  0"xl2'  0" 

Built  in  1920 


Turners  Falls  Power  & 
Electric  Co. 
Chicopee  Falls,  Mass. 
250'  0"  x  13'  0" 
Built  in  1917 


John  Stevens,  Engineer 


Virginia  Bailway  &  Power  Co., 
Richmond,  Va. 

234'  0"xl3'  0" 

Built  in  1912 


I 

I 


36 


Chapter  II 


CHIMNEYS  SUBJECTED  TO  ACID  GASES 

A  chimney  is  called  upon  to  perform  many  varied  duties  in  addition  to  pro¬ 
ducing  draft  for  steam  boilers.  This  multiplicity  of  duties  presents  many  chimney 
problems.  Ymong  them  are  the  determination  of  proper  height,  size  and  particular 
design  where  they  are  connected  with  chemical  plants,  dye  works,  smelters,  paint 
color  factories,  silvering  industries  with  their  pickling  and  plating  departments,  the 
picture  film  industry,  sintering  plants,  celluloid  factories  and  innumerable  industries, 
all  of  which  are  confronted  more  or  less  with  the  handling  of  some  form  of  acid  gases. 

Many  of  these  gases  are  destructive  to  ordinary  brick  and  mortar,  steel,  tile 
and  concrete.  Many  are  destructive  at  certain  temperatures  and  harmless  at 
other  temperatures;  destructive  with  certain  conditions  of  moisture,  but  harmless 
with  others. 

The  subject  is  an  extremely  diversified  one  requiring  not  only  a  knowledge  of 
the  mathematical  and  mechanical  features,  but  a  knowledge  of  chemistry,  thermo¬ 
dynamics,  ceramics  and  subjects  dealing  not  alone  with  the  How  of  gases,  but  with 
the  effects  of  different  kinds  of  acid  gases  under  different  degrees  of  concentration 
and  different  conditions  of  moisture  and  temperature  on  a  chimney. 

A  chimney  to  handle  noxious  and  acid  gases  must  be  designed  and  built  not 
only  for  adequate  capacity  and  draft,  but  also  to  resist  the  destructive  effect  of  the 
particular  acid  gases,  dust,  fumes  and  temperatures  and  in  addition  to  resist  the 
dynamic  wind  forces  that  tend  to  fell  it. 

Many  of  these  chimneys  are  not  operated  in  connection  with  steam  boilers,  but 
are  connected  directly  with  roasting  kilns,  furnaces  and  other  apparatus  used  in 
the  production  of  chemicals,  acids,  reduction  of  ores,  the  manufacture  of  colors, 
photo  films,  celluloid  products,  etc. 

1  he  smoke  streams  emitted  from  such  chimneys  contain  acids  in  both  liquid 
and  gaseous  form.  I  hey  are  often  reputed  to  be  a  nuisance  to  a  community. 
Some  are  supposed  to  be  detrimental  to  vegetable  and  animal  life.  Whether  or 
not  they  are  depends  entirely  upon  the  degree  of  concentration. 

Plants  of  this  nature  are  faced  with  the  disposition  ol  these  gases,  which  of 
necessity  must  pass  ofl  from  their  apparatus.  Among  the  methods  which  have 
been  used  to  remove  acid  gases  fume  and  flue  dust  from  the  smoke  are  washing 
the  smoke  streams  in  scrubbers,  the  use  of  sprays  and  baffle  chambers,  bag  houses  for 
filtration  and  electrical  precipitators,  all  more  or  less  successful  in  reducing  the 
quantity  of  fumes  and  dust.  None  have  so  far  been  successful  in  eliminating  all  the 
objectionable  elements  before  entering  the  chimney. 

Some  of  the  above  mentioned  methods  tend  to  materially  reduce  the  stack  tem¬ 
peratures.  Some  contribute  moisture  to  the  gas  stream,  increase  the  acid  mist 
and  sometimes  add  to  the  undesirable  activity  of  the  dust  and  fume. 

Chimneys  350  to  nearly  600  feet  in  height,  discharging  the  gases  at  high 
elevations  above  the  surrounding  country  where  they  become  diffused  and  diluted 
before  reaching  the  earth,  have  become  common. 


American  Smelting  &  Refining  Co. 
Tacoma,  Wash. 

57T  high  x  25'  inside  diameter  at  the  top. 
Built  in  1917.  This  chimney 
handles  acid  gases 


Eastman  Kodak  Company 
Rochester.  N.  Y. 

Two  chimneys — 366'  O'x  9'  0"  built 
in  1906  and  366'  0"xl3'  0"  built  in 
1911.  These  chimneys  handle  acid 
gases  as  well  as  gases  from  steam 
boilers 


Anaconda  Copper  Mining  Co. 
Anaconda,  Mont. 

The  largest  and  tallest  brick  chimney  in  the 
world — 585'  0"  above  ground — 60'  0"  inside 
diameter  at  the  top.  Built  in  1918.  This 
chimney  handles  acid  gases 


! 


38 


They  may  not  serve  the  purpose  perfectly,  but  their  continued  use  is  e\idence 
that  the  results  are  not  entirely  unsatisfactory. 

In  chemical  or  industrial  plants  where  the  fumes  are  not  acid,  noxious  or 
harmful,  but  yet  are  disagreeable  in  their  odor,  the  gases  are  easily  disposed  of  by 
means  of  a  comparatively  tall  chimney.  The  smoke  stream  having  no  destructive 
content,  no  precautions  need  be  taken  against  acid  action.  The  fumes  are  carried 
to  an  altitude  where  their  diffusion  in  the  atmosphere  greatly  reduces  any  objec¬ 
tionable  odors,  if  not  entirely  eliminating  them. 

The  line  dust  coming  from  roasting  kilns,  horizontal  rotary  kilns  in  the  burning 
of  lime,  pyrites,  sintering  processes,  etc.,  may  be  diffused  to  a  marked  degree  by 
emitting  the  dust  carrying  stream  at  a  high  altitude. 

Of  the  many  gases  coming  from  these  industries,  such  as  those  of  the  sulphur, 
nitric,  chlorine,  fluorin,  lead  and  arsenic  groups,  the  sulphur  group  is  the  most 
frequently  encountered. 

Those  of  the  carbon  family  give  little  concern  as  they  are  not  particularly 
detrimental  to  a  community  nor  do  they  tend  to  disintegrate  a  brick  stack. 

Sulphur  trioxide,  sulphur  dioxide,  compounds  of  lead  and  arsenious  oxide  are 
noxious  and  objectionable.  The  lirst  of  these  at  tack  to  a  marked  degree  common 
brick  and  ordinary  mortar,  concrete  and  steel  and  can  not  be  discharged  safely 
through  the  ordinary  chimney  designed  for  use  in  connection  with  steam  boilers 
burning  coal. 

Sulphur  dioxide  gas  in  the  pure  state  will  condense  to  a  liquid  at  about  1  1°  F. 
At  any  temperature  above  this  it  remains  a  gas  and  will  not  combine  to  form  a 
damp  acid  mist  nor  liquid  acid.  If  present  in  small  quantities  in  the  smoke  stream 
at  atmospheric  pressure  the  condensation  point  is  much  lower.  Therefore,  I  his 
particular  gas  has  little  or  no  effect  on  a  brick  chimney. 

At  the  present  date  it  seems  that  the  only  solution  for  the  elimination  of  the 
effect  of  sulphur  dioxide  is  to  see  that  the  sulphur  dioxide  content  of  the  smoke 
stream  is  so  diluted  before  it  reaches  the  ground  that  it  is  harmless.  This  is  being 
done  through  the  use  of  tall  chimneys  safeguarded  against  the  corrosive  action  of 
the  gases  by  means  of  auxiliary  furnaces  to  raise  I  he  temperatures.  This  is  practiced 
by  the  American  Smelting  &  Refining  Company  at  such  plants  as  require  it,  and 
is  being  adopted  by  other  companies. 

Unlike  sulphur  dioxide,  sulphur  trioxide  in  the  presence  of  water  vapor  so 
common  in  the  smoke  stream  of  the  industries  mentioned,  even  in  extreme  low 
concentrations,  will  combine  with  the  water  vapor  and  form  what  may  be  called  a 
fog  of  sulphuric  acid  or  even  liquid  sulphuric  acid  on  the  walls  of  the  chimney.  Of 
that  which  passes  out  of  the  chimney,  some  may  eventually  settle  to  the  ground  in 
the  lorni  of  sulphuric  mist  or  dew  under  certain  atmospheric  conditions,  but  the 
amount  is  so  small  in  any  properly  constructed  plant  as  to  cause  no  trouble. 

It  is  a  fact  that  the  temperatures  at  which  an  acid  gas  will  become  an  acid 
liquid  depends  largely  upon  the  concentration  of  water  vapor  and  acid  gases  in  the 
smoke  stream.  The  greater  the  concentration  of  sulphur  trioxide  and  water  vapor 


39 


-t 

A-*  ^ 


m, 


-  =-i-  _ L 


Arizona  Copper  Co.,  Clifton,  Ariz. 
300'  0"  x  22'  0".  Built  in  1912 
A  chimney  handling  acid  gases 


Consolidated  Kansas  City 
Smelting  &  Refining  Company 
El  Paso,  Texas 
■100' x  30'.  Built  in  1916 
This  chimney  handles  acid  gases. 
The  platform  gives  access  to  open¬ 
ings  in  which  instruments  are  in¬ 
serted  and  gas  samples  are  taken 


Anaconda  Copper  Mining  Co. 

Great  Falls,  Mont. 

506'  0"  x  50'  0".  Built  in  1908 
This  chimney  handles  acid  gases 


40 


r 


the  higher  the  temperature  at  which  l he  condensation  will  lake1  place.  I  n fortu¬ 
nately,  in  general,  the  sulphur  gases  handled  are  rather  dilute  and  in  the  presence  of 
moisture  are  more  active  than  a  stronger  concentrated  gas.  As  long  as  they 
remain  a  gas,  or  in  other  words,  as  long  as  the  sulphur  trioxide  is  kept  at  a  tem¬ 
perature  over  100°  F.  they  have  little  effect  upon  hard  burned  impervious  brick 
or  so-called  commercial  acid-proof  mortar.  Some  authorities  give  the  condensation 
point  of  the  sulphur  trioxide  under  the  above  conditions  as  low  as  275°  F.  The 
best  practice  is  to  maintain  a  temperature  of  the  smoke  stream  of  400°  F.  or  over. 
It  will  be  noticed  that  these  temperatures  are  above  the  boiling  point  of  water. 

The  fumes  of  chlorine  and  nitrous  oxide  under  certain  conditions  attack 
common  brick  and  mortar,  concrete,  unvitrified  tile,  steel  and  the  common  metals. 

The  effect  on  these  materials,  particularly  in  the  presence  of  moisture  and  low 
temperatures,  is  practically  the  same  as  the  effect  of  sulphur  trioxide. 

A  structure  to  stand  up  against  them  should  follow  the  same  general  design 
and  use  of  materials  as  one  built  to  resist  the  action  of  sulphuric  acid. 

The  disposition  of  the  chlorine  and  nitrous  oxide  fumes,  by  emitting  them  at 
high  altitudes,  is  common  practice. 

Here,  too,  if  the  products  of  combustion  carrying  these  two  gases  have  a  lowr 
temperature,  auxiliary  furnaces  lired  at  the  foot  of  the  stack  are  employed  to  raise 
the  temperature,  give  impetus  or  added  velocity  to  the  smoke  stream,  decrease  its 
density  and  cause  it  to  raise  to  considerable  heights  above  the  top  of  the  chimney. 
The  diffusion  in  the  atmosphere  is  thus  more  completely  accomplished. 

The  most  important  thing  in  handling  acid  gases  in  a  chimney  is  to  maintain 
a  high  internal  temperature.  This  often  destroys  the  detrimental  effect  of  the 
gases  on  the  masonry.  Furthermore,  the  higher  the  temperatures  of  the  emitted 
gases  at  the  top  of  the  stack,  the  higher  the  fumes  and  fine  acid  dust  will  ascend, 
consequently  their  greater  diffusion  before  reaching  the  ground.  This  is  a  most 
important  fact  to  the  management  of  smelters  and  chemical  plants,  especially 
where  they  have  sulphur  dioxide  to  contend  with. 

A  wet  or  damp  acid  smoke  stream  in  contact  with  ordinary  mortars  made  of 
cement,  lime  and  sand,  or  sand  and  cement,  and  certain  commercial  mortars  which 
do  not  contain  cement  and  lime,  produces  a  swelling  and  puffing  of  both  the  bed 
and  cross  joints  accompanied  by  a  tremendous  pressure.  The  swelling  amounts 
at  times  to  25  to  30  per  cent. 

A  chemical  change  takes  place  at  first  on  the  surface.  The  mortar  becomes 
soft  and  of  the  consistency  of  mud.  As  time  goes  on  this  softening  and  swelling 
w  orks  entirely  through  the  w  alls,  causing  the  brick  w  ork  to  bulge  and  crack.  Steel 
bands  are  useless,  even  on  the  outside,  for  the  masonry  will  bulge  betw  een  the  bands 
and  in  time  the  bands  will  give  w  ay.  If  the  temperatures  are  raised  or  the  chimney 
dries  out  the  inner  portion  of  the  joints  may  become  hardened  but  still  remain 
swelled.  If  the  brick  is  not  hard  and  impervious  the  exposed  portion  becomes 
soft  and  flakes  off.  This  process  continues  until  the  whole  brick  is  changed  into 
a  soft  mass. 


n 


Design  of  chimney  for  acid  gases.  Indepen¬ 
dent  acid-proof  lining  in  the  round  column. 
Acid-proof  corbel  lining  in  the  base.  Corbels 
and  air  space  protected  with  lead  aprons. 
Lead  cap  on  the  head  and  top  of  lining 


Fig.  28  — -  Chimney  with  sectional  lining 
for  handling  acid  gases 


C.  K.  Williams  &  Co. 
Easton,  Pa. 

375'  0"  x  7'.  Built  in  1911 
This  chimney  handling  acid  gases 


Cases  have  been  observed  where  the  swelling  of  l lie  joints  is  quite  uniform  in 
the  circumference  of  the  chimney  and  irregular  bulging  of  the  structure  hardly 
discernible.  The  disintegration  takes  the  form  of  vertical  cracks.  These  usually 
appear  first  at  the  top  where  the  walls  are  thinnest  and  in  time  they  work  downward 
to  the  base.  The  vertical  cracks  are  due  to  the  swelling  of  the  joints  causing  cir¬ 
cumferential  strains  as  the  diameter  tends  to  increase.  These  strains  are  greater 
than  the  strength  of  the  masonry.  It  is  further  observed  that  the  cracks  increase 
more  rapidly  and  become  larger  on  the  prevailing  windward  or  weather  side. 
This  is  to  be  expected,  for  on  that  side  the  rain  and  snow  are  driven  more  frequently, 
and  more  forcibly,  against  the  surface  and  into  the  interior  of  the  initial  small  cracks. 
The  water  enhances  the  disintegration  of  the  acid-soaked  joint.  Once  the  joints 
are  soaked  with  the  acid,  the  swelling  will  continue  as  long  as  they  can  take  up  any 
moisture,  and  by  capillary  attraction  this  continues  to  spread  through  large  areas. 

Even  if  the  acid  fumes  are  not  wet,  but  are  dry,  certain  of  them  will  attack  the 
above  mentioned  mortars,  destroy  the  cement  or  any  binder  that  contains  an 
element  which  will  combine  with  the  acid  fumes,  turning  the  joint  into  a  weak 
sandy  mass.  Bricks  not  vitrified  and  impervious  share  the  same  fate.  The  effect 
on  concrete  is  a  rapid  disintegration  of  the  whole  mass,  due  to  the  breaking  up  of 
the  cement  content,  and  the  acid  action  on  certain  aggregates. 

Acid  action  has  been  observed  from  the  smoke  stream  resulting  from  the 
burning  of  certain  fuel  oils  under  boilers.  This  is  particularly  in  evidence  w  here  the 
sulphur  content  of  the  oil  is  high  and  steam  atomizing  burners  are  used.  In  these 
installations,  especially  in  connection  with  economizers  resulting  in  low  Hue  tem¬ 
peratures,  and  when  the  chimneys  are  high,  the  protection  of  the  upper  portion 
should  have  the  attention  of  a  designing  engineer.  It  all  depends  upon  the  sulphur 
content  of  the  oil  and  the  tine  temperatures. 

Smoke  from  many  fuel  oils  has  no  effect  on  the  brick  lining  designed  for  coal 
burning  steam  boilers. 

In  designing  a  chimney  for  acid  duty  it  is  necessary  to  perfectly  protect 
the  main  walls  by  an  independent  lining  for  the  full  height  of  the  structure,  with  an 
ample  air  space  between  it  and  the  main  walls.  An  air  space  of  not  less  than 
3  or  4  inches  at  any  point  is  recommended.  In  fact  the  design  is  a  chimney  w  ithin 
a  chimney.  See  drawing,  Figure  27,  page  42 

The  independent  inner  lining  must  be  built  of  impervious,  practically  vitrified, 
brick,  very  low  in  lime  and  laid  up  in  acid-proof  mortar :  i.  e.,  an  acid-proof  mortar 
made  to  resist  the  particular  kind  of  acid  in  the  smoke  stream.  The  thinnest  pos¬ 
sible  joint  is  imperative.  The  bricks  should  be  thinly  buttered  or  dipped  and 
struck  tightly  into  place. 

Many  commercial  acid-proof  mortars  are  acid-proof  against  certain  acids  so 
long  as  the  acid  gases  are  dry  and  of  a  comparatively  high  temperature.  These  are 
often  composed  of  a  mixture  of  pure  clay,  silica  sand  or  silex,  kaolin,  asbestos 
fibre,  china  clay,  graphite  products,  ground  gypsum  and  the  like.  A  common 
binder  is  silicate  of  soda.  These  mixtures  are  not  always  acid-proof  and  often 


43 


break  up  under  the  action  of  moisture.  They  soften, 
swell  and  disintegrate  under  a  wet  acid.  So  the 
mortar  must  not  only  be  acid-proof  but  be  moisture- 
proof.  Sand  only  of  practically  a  pure  silica  content 
should  be  used. 

The  top  of  the  chimney  should  be  protected 
with  a  cap,  covering  both  the  lining  and  the  main 
walls,  and  made  of  material  not  affected  by  the  par¬ 
ticular  kind  of  acid  under  consideration.  Ample 
room  should  be  allowed  for  the  lining  to  expand 
upward  and  outward. 

Furthermore,  the  cap  should  be  so  designed  that 
no  dust,  fumes  or  moisture  can  find  their  way  down 
between  the  main  walls  and  the  lining.  It  will  be 
noted,  with  this  design,  the  lining  has  room  to  ex¬ 
pand  upward  without  lifting  the  cap.  The  air  space 
is  protected.  See  drawing,  Fig.  29. 

With  certain  acid  conditions  the  cap  may  be 
made  of  lead.  On  the  other  hand  certain  acids  wi 
lead — not  necessarily  disintegrate  it,  but  cause  it  to  buckle. 
With  other  acid  conditions  a  cap  of  monel  metal  has  been 
used  with  success.  The  choice  of  material  is  dependent 
entirely  upon  the  nature  of  the  acid. 

The  gases  coming  from  the  top  of  a  chimney  are  often 
blown  down  the  outside  for  distances  varying  from  25  to  100 
feet.  For  that  reason  the  same  acid-proof  mortar  used  in 
the  lining  should  be  used  on  the  outside  joints  of  the  upper 
portion  of  the  main  walls.  Since  this  surface  is  exposed 
to  the  weather  it  is  most  necessary  that  the  mortar  be 
weather-proof.  Common  building  lime  should  never  be  used 
in  any  part  of  the  structure. 

In  some  cases  where  the  temperature  of  the  acid  smoke 
stream  is  continually  high,  and  the  acids  not  very  active,  the 
same  brick  and  mortar  may  be  used  and  a  sectional  lining 
constructed  in  place  of  an  independent  lining.  See  drawing, 
Fig.  28,  page  42.  This  form  of  construction  is  less  ex¬ 
pensive.  The  corbels  built  out  at  intervals  from  the  main 
walls  and  supporting  the  lining  should  have  the  inner  joints 
pointed  with  acid-proof  mortar. 

On  the  top  of  each  corbel  an  apron  of  an  acid-proof 
material  should  be  set  in  such  a  manner  that  the  lower  lip 
projects  down  over  the  top  of  the  section  of  lining  below. 
The  air  space  is  then  protected.  In  addition  to  this  the 


Note  expansion  space  at  top  of  lining 

-At- 

11  affect 


— v- 

X 

\AN 

,  \ 

V\ 

z: 

<r> 

\V 

4. 

\ 


Fig.  30 

Detail  of  supporting  corbel 
showing  protecting  apron 
and  expansion  space  for 
lining 


44 


upper  12  inches  or  so  of  the  air  space  under  each  corbel  should  he  packed  with 
flexible  material  not  affected  by  the  particular  acid  encountered.  See  drawing, 
Fig.  30,  page  -11. 

Where  lightning  rods  are  installed  on  acid  chimneys,  the  upper  50  feet  or  more 
of  the  complete  rod  should  be  sheathed  to  protect  the  copper  from  effects  of  the 
acid.  Lead  covering  is  in  most  cases  effective. 

All  chimneys  handling  acid  gases  should  be  equipped  with  an  outside  ladder, 
the  upper  portion  of  w  hich  should  be  covered  with  lead  or  an  acid-resisting  material. 

Chimneys  that  have  been  in  practically  continuous  service  for  years  without 
show  ing  any  effect  from  the  smoke  stream  have  been  observed  to  develop  defects, 
particularly  in  the  upper  portions,  after  they  have  been  shut  down  for  a  protracted 
period. 

Although  t he  conditions  of  temperature,  dilution,  acid  mixture  and  the  like 
may  be  such  as  not  to  cause  damage  while  the  chimney  is  in  operation,  yet  an 
accumulation  of  dust  on  the  inner  walls,  which  is  deliquescent  by  virtue  of  its 
acid  content,  may  tend  to  do  damage  when  the  chimney  is  not  in  operation. 

The  weather,  rain,  fog,  snow  or  a  heavy  humid  atmosphere  furnishes  the 
necessary  w  ater  within  the  chimney  to  convert  the  previously  inert  dust  with  an 
acid  content  into  a  liquid  acid  which  immediately  becomes  active. 

It  is,  therefore,  wise  when  the  chimney  is  shut  down  for  a  period  to  cover  the 
entire  opening  at  the  top  with  a  temporary  weather-proof  lid.  This  can  be  made 
in  sections  of  light  wood  easily  placed  and  removed.  Lugs  protected  against  acid 
action  should  be  built  into  the  head  to  which  the  sections  of  the  temporary  lid 
may  be  fastened. 

A  good  arrangement  in  designing  a  plant  in  which  acid  fumes  are  to  be  carried 
off  is  to  locate  the  boiler  house  so  that  the  gases  from  the  boilers  and  the  acid  fumes 
from  the  apparatus  can  be  put  in  the  same  chimney.  Such  an  arrangement  is  in 
use  at  the  Murray  Plant  of  the  American  Smelting  &  Refining  Company  and  at 
the  Eastman  Kodak  Company,  Rochester,  N.  Y. 

The  boiler  gases  not  only  keep  the  temperatures  up,  but  they  dilute  the  smoke 
stream  containing  acid  gases. 

No  haixl  and  fast  rules  can  be  laid  down  which  will  apply  to  every  case  where 
chimneys  handle  acid  gases.  The  problem  of  design  and  materials  used  can  be 
solved  only  by  an  intimate  knowledge  of  the  nature  and  effect  of  the  particular 
fumes  or  dust  to  be  disposed  of. 


45 


The  Tallest  and  Largest  Chimneys  in  the  World  Have  Been  Built 
by  the  Alphons  Custodis  Chimney  Construction  Company.  Most  of 
These  Chimneys  Handle  Vcid  Gases. 


Anaconda  Copper  Mining  Company, 
Anaconda,  Mont. 

585'  above  grade.  60'  inside  diameter  at  top. 

Built  in  1918. 

American  Smelting  &  Refining  Co., 
Tacoma,  Wash. 

571'  0"  x  25'  Built  in  1917. 

Anaconda  Copper  Mining  Co. 

Great  Falls.  Mont. 

506' x  50'  Built  in  1907. 

Federal  Bead  Company, 

Federal,  Ill. 

450'  x  17'  0"  Built  in  1923. 

United  \  erde  Extension  Mining  Co., 
Jerome,  Ariz. 

425' x  30'  0"  Built  in  1918. 

United  Verde  Copper  Co., 

Clarkdale,  Ariz. 

430'  x  29'  0"  Built  in  1922. 

Consolidated  Kansas  City  S.  &  B.  Co., 

El  Paso,  Texas. 

400' x  30'  0"  Built  in  1916. 

American  Smelting  &  Refining  Co., 
Hayden,  Ariz. 

300'  x  25'  0"  Built  in  1911. 

American  Smelting  &  Refining  Co., 

E.  Helena,  Mont. 

400'  x  16'  0"  Built  in  1917. 

American  Smelting  &  Refining  Co., 
Garfield,  Utah. 

300'  x  30'  0"  Built  in  1905. 


Garfield  Smelting  Company, 

Garfield,  Utah. 

350'  x  22'  Built  in  1913. 

C.  K.  Williams  Company, 

Easton,  Pa. 

375'  x  7'  Built  in  1911. 


Eastman  Kodak  Company, 
Rochester,  N.  Y. 

1-366' x  9'  Built 

1-366' x  13'  Built 

1-350' x  17'  Built 


in  1906. 
in  1911. 
in  1920. 


Heller  Mertz  Company, 

Newark,  N.  J. 

350' x  8'  Built  in  1904. 

Public  Service  Co.  of  Colorado, 

Valmont,  Col. 

350'  x  16'  Built  in  1923. 


Magna  Copper  Company, 
Superior,  Ariz. 

300'  x  20' 

New  Jersey  Zinc  Company, 
Austinville,  Ya. 

350'  x  5' 


Built  in  1923. 


Built  in  1920. 


General  Chemical  Company, 

Claymont,  Del. 

300' x  8'  Built  in  1912. 

Nichols  Chemical  Company, 

Brooklyn,  N.  Y. 

300'  x  12'  Built  in  1905. 

Pyrites  Company, 

Wilmington,  Del. 

300' x  12'  Built  in  1919. 


46 


r 


I 

I 

I 


Federal  Lead  Co., 
Federal,  Ill. 

450'  x  17'  Built  in  1923 

This  chimney  handles  acid  gases 


United  Verde  Copper  Co., 
Clarkdale,  Ariz. 

430'  x  29'  Built  in  1922 

This  chimney  handles  acid  gases 


H.  .1.  Heinz  Co., 
Pittsburgh,  Pa. 

250'  x  10'  Built  in  1919 


Pacific  Mills, 
Groce.  S.  C. 

175'  x  9'  Built  in  1923 


Chapter  III 


ELEMENTS  IN  DETERMINING  THE  PROPER  SIZE  OF 
CHIMNEY  FOR  A  SPECIFIC  INSTALLATION 


The  subject  of  draft,  draft  losses  and  the  proportioning  of  chimneys  is  one 
upon  which  an  entire  volume  could  be  written.  As  a  book  of  this  nature  does 
not  admit  of  an  exhaustive  discussion,  we  will  set  forth  only  the  basic  principles 
of  theory  and  modern  engineering  practice. 

Most  of  the  formulas  for  determining  chimney  sizes  are  empirical.  These 
generally  give  satisfactory  results  provided  they  are  used  within  the  limits  of 
the  assumptions  upon  which  they  are  based,  or  in  other  words,  one  must  have 
definite  knowledge  applicable  to  the  specific  problem. 

The  height  and  diameter  of  any  chimney  is  determined  by  considering:  first, 
the  amount  of  draft  required;  second,  the  requisite  and  economical  velocity;  and 
third,  the  maximum  quantity  of  gas  that  must  pass  out  ol  the  chimney. 

The  available  draft  is  equal  to  the  difference  in  the  weight  of  the  cold  column 
of  external  air  and  a  like1  column  ol  hot  gas  in  the  chimney  minus  the  loss  due  to 
internal  friction  and  the  loss  due  to  accelerating  the  gases.  I  he  height  therefore 
depends  upon  the  available  draft  required  and  may  be  influenced  by  the  diameter. 

The  theoretical  draft  of  a  chimney  100  feet  high  at  sea  level  is  given  in  Table  3, 
expressed  in  inches  of  water.  I  liese  values  were  calculated  from  the  lormula: 


MTD  =  H 


Where  MTD  =the  maximum  theoretical  draft 


H  =  height  in  feet 

Ti=average  absolute  temperature  (°  F.)  of  the  flue  gases 
T  =  absolute  temperature  (°  F.)  of  outside  air. 

The  absolute  temperature  (°  F.)  is  equal  to  the  temperature  reading  (°  F.) 
plus  161  F. 

The  formula  is  based  on  the  fact  that  the  theoretical  draft  is  equal  to  the 
difference  in  the  weight  of  the  cold  column  ol  air  outside  the  chimney  and  the 
hot  column  of  gas  inside  the  chimney — i.  e.,  the  theoretical  draft  =  H  (weight  per 
cubic  foot  of  the  outside  air  at  the  given  temperature  minus  the  weight  per  cubic 
foot  of  the  flue  gas  at  the  given  temperature)  X0.192;  where  0.192  is  the  constant 
for  converting  to  inches  of  water  from  pounds  per  square  foot. 


TABLE  NO.  3 

THEORETICAL  DRAFT  PRESSURE  IX  INCHES  OF  WATER  IN  A  CHIMNEY  100' 0"  HIGH 


Temp,  in  |  Temperature  of  External  Air  (Barometer  30') 


Chimney 

Fahr. 

0° 

10° 

20° 

30° 

40° 

50° 

60° 

70° 

80° 

90° 

100° 

200° 

.453 

.419 

.  384 

.353 

.321 

.292 

.263 

.234 

.209 

.  182 

.157 

220° 

.488 

.453 

.419 

.388 

.  355 

.326 

.298 

.269 

.  244 

.217 

.  192 

240° 

.520 

.488 

.451 

.121 

.  388 

.  359 

.330 

.301 

.  275 

.  250 

•  225 

260° 

.528 

.484 

.453 

.420 

.392 

.363 

.  334 

.  309 

.282 

.  267 

280° 

.584 

.549 

.515 

.482 

.451 

.  122 

.394 

.  365 

.340 

.313 

.  288 

300° 

.611 

.541 

.51 1 

.478 

.419 

.420 

.392 

.367 

.  340 

.  315 

320° 

.637 

.603 

.  568 

.538 

.  505 

.476 

.  447 

.419 

.394 

.  367 

.  342 

340° 

.662 

.638 

.593 

.563 

.  530 

.501 

.472 

.  443 

.419 

.392 

.  367 

360° 

.687 

.618 

.588 

.  555 

.526 

.497 

468 

.4  44 

.417 

.392 

380° 

.710 

676 

.641 

.611 

.578 

.549 

.520 

.  192 

.467 

.440 

.415 

400° 

.732 

.697 

662 

.632 

.598 

.570 

.541 

.513 

488 

.  461 

.  436 

420° 

.718 

.684 

.653 

.620 

.591 

.563 

.  534 

.  509 

.482 

.  457 

440° 

.774 

.739 

.705 

.674 

.641 

612 

.584 

.  555 

.  530 

.503 

.478 

460° 

.793 

.758 

.724 

.694 

.  660 

.632 

.603 

.574 

.  549 

.522 

.  497 

480° 

.810 

.776 

.741 

.710 

.678 

.649 

.620 

.591 

.  566 

.  540 

.515 

500° 

.829 

.791 

.760 

.730 

.697 

.669 

.639 

.610 

.586 

.  559 

.  534 

.863 

.828 

.795 

.762 

.731 

.700 

.671 

.  64  1 

.618 

.  593 

.  585 

600° 

908 

.87.3 

.839 

.807 

.776 

.746 

.717 

.690 

.  663 

.  638 

.613 

48 


Iii  Table  3,  for  any  oilier  height  of  chimney,  multiply  these  values  by 
where  II  is  the  height  in  feet. 

The  weight  of  gas  which  will  pass  up  the  chimney  increases  as  the  temperature 
of  the  flue  gas  increases,  but  maximum  is  reached  according  to  Rankin  at  about 
622°  F.,  as  at  any  internal  temperature  above  that,  the  gas  velocity  increases  less 
than  the  density  of  the  gases  decreases. 

In  the  draft  formula  the  average  temperature  is  used  because  tests  show  that 
the  temperature  of  the  gases  at  the  top  of  the  chimney  is  less  than  it  is  at  the 
bottom.  The  amount  of  drop  in  temperature  depends  upon  the  dimensions  of  the 
chimney,  the  material  of  which  it  is  built  and  the  volume  of  the  gases.  In  tall 
chimneys  of  large  diameter  the  drop  in  temperature  is  usually  less  than  it  is  in 
tall  chimneys  of  small  diameter.  In  unlined  steel  stacks  the  drop  is  greater, 
especially  with  low  external  temperatures. 

Unfortunately  there  have  not  been  many  tests  made  to  determine  actual 
chimney  performance  and  the  engineering  profession  is  in  need  of  further  infor¬ 
mation  on  this  subject.  Facilities  for  observation  have  been  provided  by  the 
Custodis  Co.  at  three  elevations  on  the  chimney  225'  x  1 1/  0"  constructed  in  1  (>2.> 
at  Cornell  University,  Ithaca,  N.  \.,  on  the  chimney  175' x  10' 0"  constructed 
1923  at  the  Oregon  Agricultural  College,  Corvallis,  Ore.,  on  the  chimney  ot  the 
Public  Service  Co.  of  Col.,  Valmont,  Col.,  350'  x  16'  0"  built  in  1921  and  also  on  the 
common  brick  chimney  150' x  7' 0"  constructed  in  1911  at  Johns  Hopkins  Uni¬ 
versity,  Baltimore,  Md. 

Figure  31  gives  some  results  of  the  observations  on  the  drop  in  temperature 
as  the  gases  move  upward  in  Custodis  brick  chimneys  deduced  Irom  observations 
by  Peabody  and  Miller  and  J.  C.  Smallwood. 


Height  of  chimney  in  feet 


Fig.  31 

Average  temperatures  of  gases  in  per  cent  of  entering  temperature 
according  to  height 


19 


Example  I. — To  determine  the  maximum  theoretical  draft  produced  by  a 
circular  brick  chimney  200  feet  high  at  sea  level,  average  temperature  of  hue  gases 
600°  F.,  and  the  outside  air  temperature  60°  F. 

Atmospheric  pressure  at  sea  level  =  1 1.7  pounds  per  square  inch 

MTD  =  H  (^4r~ ~ 

\  T  Ti 

W  here  T  =  60+  161  =521 
Ti  =600+461  =  1061 


MTD  =200 


7.61  7.95  \ 
521  1061/ 


MTD  =1.134" 

At  atmospheric  pressure  and  an  external  temperature  of  60°  F.  the  values  of 


the  expression 


7.61  7.95 

521  T, 


have  been  calculated  and  tabulated  for  various 

Then  MTD  =  H J 


internal  chinmex  temperatures  and  max  be  found  in  Table  1. 
where  J  is  the  table  x  alue. 


TABLE  I 

/ 7 . 6  I  7.95\ 

\  alue  of  (  -  0  j  —  I  for  \  arious  Internal  Temperatures  for  One  Foot  of  Height 
Temperature  of  External  Air — 60°  F.  Barometer — 11.7  Pounds  per  Square  Inch 


Temperature  in 

Chimney. .  .  . 

.  .  200° 

220° 

210° 

260° 

280° 

300° 

320° 

340° 

360° 

(7.61 

J.97,\ 

. 00263 

. 00298 

f  521 

Ti  / 

Temperature  in 

380° 

400° 

420° 

1  10° 

460° 

480° 

500° 

550° 

600° 

7.95X 

. 00520 

.00541 

. 00563 

. 0058 l  j 

. 00603 

00639  i 

1  521 

'l  l  ) 

The  available  draft  in  a  well-designed  chimney  at  the  breeching  opening  may 
be  safely  assumed  as  80%  of  the  theoretical.  A  small  number  of  tests  on  com¬ 
paratively  high  chimneys  gave  results  close  to  this  value.  The  coefficient  of  friction 
in  masonry  chimneys  has  not  been  definitely  ascertained.  In  viewT  of  this,  the 
xmlue  of  ”80%"  is  probably  as  nearly  correct  as  the  values  calculated  from  the 
numerous  formulas.  It  is  hoped  that  tests  at  Cornell  University,  Oregon  State 
Agricultural  College  and  Johns  Hopkins  University  will  give  some  further  light 
on  this  subject. 

The  formula  then,  for  maximum  available  draft,  at  sea  level  is 

MAD  =HJX  0.80 

Where  MAD  =  maximum  available  draft 


The  ax  ailable  draft  required  is  determined  by  taking  draft  gauge  readings  on 
installations  similar  to  the  one  proposed.  In  the  event  that  this  is  not  possible, 
the  proposed  installation  should  be  analyzed  in  the  light  of  past  experience  and 
the  available  draft  required  estimated. 


50 


II'  the  chimney  is  located  near  a  high  hill  or  building,  it  may  be  necessary  to 
increase  the  height  because  the  wind  may  decrease  the  available  draft  when  it 
blows  from  the  direction  of  the  barrier. 

The  required  area  is  obtained  by  dividing  the  volume  of  gases  emitted  by  the 
assumed  velocity. 

With  the  total  weight  and  analysis  of  the  fuel  burned  and  the  Hue  gas  analysis 
known,  the  total  weight  or  volume  of  the  Hue  gases  can  be  calculated. 

For  ordinary  calculations  the  following  velocities  have  been  recommended. 
They  may  be  safely  used  for  the  following  quantities  of  gases  without  undue 
friction  losses  in  the  chimney  or  prohibitive  cost  of  construction. 


Gases, 

Lbs.  per  Hr. 
3,600. 
55,750 . 
120,900. 
2  17,000. 
559,000 . 
1.105,000. 


Velocity, 
Ft.  per  Sec. 
10 
15 
20 
25 
30 
35 


CHIMNEY  AT  ALTITUDES  ABOVE  SEA  LEVEL 

As  the  altitude  above  sea  level  increases  the  barometric  pressure  decreases,  or 
in  other  words,  I  lie  weight  of  air  per  cubic  foot  is  less.  There  is  some  difference 
of  opinion  as  to  the  correct  method  for  calculating  the  height  of  chimney  at  alti¬ 
tudes.  However,  the  method  commonly  used  of  multiplying  the  height  required 
at  sea  level  by  the  ratio  of  the  barometer  reading  at  sea  level  to  the  barometer 
reading  at  altitude  has  given  good  results. 

The  number  of  pounds  of  air  required  to  burn  a  pound  of  any  given  fuel  is 
the  same,  regardless  of  the  altitude.  Therefore  it  is  obvious  that  the  volume  of 
air  furnished  for  combustion  and  I  he  resultant  volume  of  Hue  gas  must  increase 
as  the  barometric  pressure  decreases. 

It  is  evident  that  w  hen  the  height  of  I  he  chimney  and  volume  of  gas  are  increased, 
the  friction  loss  is  increased.  In  order  that  the  same  draft  may  si  ill  be  available 
as  at  sea  level,  it  will  be  necessary  to  increase  the  diameter  proportionately. 
Reliable  authorities  state  that  the  diameter  should  vary  as  the  two-fifths  power 
of  the  ratio  of  the  barometer  reading  at  sea  level  to  the  barometer  reading  at 
altitude. 

Table  5  has  been  compiled,  giving  the  barometric  pressure  at  different  eleva¬ 
tions,  the  ratio  of  the  pressures  and  the  value  of  the  two-fifths  power  of  the  ratio. 

It  is  observed  that  the  drop  in  barometric  pressure  affects  the  height  very 
much  more  than  the  diameter.  Up  to  the  altitude  of  2,500'  or  3,000',  though  the 
height  should  be  increased,  no  increase  of  diameter  is  necessary  for  practical 
purposes. 


Where  the  altitudes  are  unusually  high,  the  available  draft  required  is  reduced 
by  changing  the  plant  design,  lowering  the  combustion  rate  and  increasing  the 
size  of  tire  flues.  If  this  were  not  done,  a  very  large  chimney  would  be  required 
to  give  the  desired  results. 

TABLE  5 

CHIMNEYS  AT  ALTITUDES  ABOVE  SEA  LEVEL 
Correction  Factors 


Altitude  in 

Feet  Above 
Sea  Level 

Barometer 
Beading 
in  Inches 

R 

Relative 

Gas  Volume 

R  2/5 

Ratio  Chimney 
Diameters 

Altitude  in 
Feet  Above 
Sea  Level 

Barometer 
Reading 
in  Inches 

R 

Relative 

Gas  Volume 

R  2/5 

Ratio  Chimney 
Diameters 

0 

30 . 00 

1 . 000 

1  000 

4,500 

25 . 45 

1.180 

1  068 

500 

20 , 46 

1.019 

1  008 

5,000 

21  98 

1.201 

1  076 

1,000 

28  92 

1 . 037 

1  015 

5,500 

24 . 53 

1 . 224 

1  084 

1,500 

28  40 

1 . 057 

1  023 

6,000 

24  08 

l  246 

1  092 

2,000 

27 . 88 

1 . 076 

1  .030 

6,500 

23 . 65 

1 . 269 

1  100 

2,500 

27 . 38 

1 . 006 

1  ,  038 

7,000 

23 . 22 

1.292 

1  108 

3,000 

26 . 88 

1,116 

1  045 

8,000 

22.38 

1 . 340 

1  124 

3,500 

20 . 10 

1 . 137 

1 . 053 

9,000 

21  .58 

1 . 390 

1  111 

4.000 

25  01 

1.158 

1  060 

1  0.000 

20  80 

1  442 

1  158 

Example  II. — To  determine  the  size  of  chimney  required  at  an  elevation  of 
6500,  assuming  that  a  given  installation  requires  a  chimney  180'  x  7'  6"  at  sea  level 
and  the  available  draft  required  is  the  same. 

Normal  barometer  at  sea  level  =30.000 
Barometer  at  6500'  =23.65 

Ratio  between  the  pressures  R  =  1.269 

Height  of  chimney  =  180  X  1.269  =228  feet. 

The  two-fifths  power  of  ratio  of  the  two  pressures  =  1.100. 

Diameter  of  chimney  =7.5  X  1.100  =8'  3" 

Hence  a  chimney  228' x8'  3"  is  required. 

At  2000'  altitude  the  chimney  height  would  be  180x1.076  =  194  feet,  with 
practically  no  change  in  diameter  necessary. 

The  fuels  generally  used  in  the  United  States  are  coal,  oil  and  wood. 

Coals  are  classilied  in  several  ways,  but  for  the  purposes  of  this  article  they 
can  be  designated  as  anthracite,  semi-bituminous,  bituminous,  and  lignite. 

Anthracite  coal  contains  approximately  92%  fixed  carbon  and  6%  volatile 
matter  and  has  an  approximate  heat  value  of  15,000  R.  t.  u.  per  pound  of  com¬ 
bustible.  Anthracite  coal  is  in  great  demand  for  domestic  purposes  and  only  the 
smaller  sizes  are  available  for  industrial  uses.  Some  form  of  forced  draft  is  ordi¬ 
narily  used  to  burn  the  line  sizes  of  anthracite  coal  now  available. 

Semi-bituminous  coal  contains  approximately  79%  fixed  carbon,  2'2y2c/0  volatile 
matter,  and  has  a  heat  a  alue  of  approximately  1  4,000  R.  t.  u.  per  pound  of 
combustible. 

Bituminous  coal  varies  widely  in  composition,  ranging  from  45%  to  70% 
fixed  carbon  and  25%  to  50%  volatile  matter.  It  has  a  heat  value  ranging  from 
9,000  B.  t.  u.  to  1 4,500  B.  t.  u.  per  pound  of  combustible.  It  does  not  stand 
handling  vrell  and  the  fine  sizes  or  slack  frequently  have  to  be  burned.  If  so, 
ample  draft  should  be  provided. 

Lignite  coal  also  has  a  varying  composition  ranging  from  25%  to  35%  fixed 
carbon  and  27%  to  32%  volatile  matter.  It  lias  a  heat  value  ranging  around 


12,500  B.  t.  u.  [KT  pound  of  combustible.  Lignite  coni  contains  a  large  amount  ol 
moisture  and  is  likely  to  air  slack. 

Coal  is  burned  upon  hand  lired  grates,  in  stokers  and  in  the  pulverized  form. 
The  quantity  of  air  theoretically  required  for  combustion  is  practically  constant 
in  the  ratio  of  7.6  pounds  of  air  per  10,000  B.  t.  u.  However,  the  percentage  of 
excess  air  required  increases  rapidly  as  the  quality  of  the  coal  decreases,  except  in 
the  case  of  pulverized  coal.  The  percentage  of  excess  air  required  for  pulverized 
coal  is  very  low,  as  the  combustion  is  readily  completed. 

The  heat  value  of  commercial  fuel  oil  ranges  from  17,500  B.  t.  u.  to  19,000 
B.  t.  u.  per  pound,  and  that  of  crude  oil  ranges  up  as  high  as  22,000  B.  t.  u.  Crude 
oil  is  seldom  used,  as  it  is  much  more  expensive.  The  oil  burners  atomize  the  oil 
into  a  very  finely  divided  spray,  consequently  only  a  small  per  cent  of  excess  air 
is  required.  The  quantity  of  air  theoretically  required  for  combustion  varies  with 
the  amount  of  hydrogen  in  the  fuel.  Approximately  14  pounds  of  air  per  pound 
of  oil  are  required  for  this  purpose. 

Wood  shavings,  sawdust,  tan  bark  and  bagasse  are  by-products  having  varying 
heat  values  depending  upon  their  origin. 

In  the  average  plant  burning  by-product  fuels  the  calculation  of  the  volumes 
of  resultant  gases  to  a  fine  degree  of  accuracy  is  hardly  possible.  The  fuel  has  no 
commercial  value;  as  a  result  no  great  attempt  is  made  to  operate  efficiently.  This 
means  widely  fluctuating  excess  air  percentages.  In  addition  to  this  the  quality 
of  fuel  varies  widely  from  time  to  time  in  the  same  plant.  The  determining  of 
the  volumes  of  resultant  gases  is,  therefore,  largely  a  matter  of  experience  with 
the  peculiar  conditions  under  consideration. 

The  various  kinds  of  by-product  fuel  are  generally  burned  in  extension  furnaces 
provided  with  large  combustion  space  and  plenty  of  heated  brickwork  to  radiate 
heat  to  the  fuel  bed  and  evaporate  the  moisture.  The  ordinary  practice  is  to  allow 
the  fuel  to  pile  up  in  cones  three  to  six  feet  high.  One  very  successful  furnace 
employs  forced  draft  under  the  grates. 

CHIMNEYS  IN  CONNECTION  WITH  STEAM  BOILER 
PLANTS  BURNING  COAL 

The  accuracy  of  formulas  to  determine  stack  sizes  for  boiler  plants  evolved 
by  early  authorities  depended  mainly  upon  the  value  of  certain  constants.  The 
fixing  of  proper  values  for  these  constants  with  any  degree  of  accuracy  is  almost 
an  impossibility.  Consequently  it  has  not  been  found  practical  to  apply  them 
generally  to  chimney  design.  For  this  reason  many  engineers  have  resorted  to  rule 
of  thumb  with  results  not  entirely  unsatisfactory,  yet  they  may  err  one  way  or 
the  other. 

The  well-known  and  generally  accepted  formulas  of  W  m.  Rent,  frequently 
applied,  accord  well  with  the  good  results  of  actual  practice,  particularly  when 
overloads  are  not  high. 


The  dimensions  of  a  chimney  should  not  be  taken  from  a  table  or  calculated 
from  a  formula  and  be  accepted  as  final  without  computing  the  size  on  a  maximum 
gas  basis  and  total  draft  loss  basis,  using  the  method  previously  discussed.  Yet  it 
is  helpful  and  interesting  to  compare  a  tabulated  11.  P.  size  with  one  computed  on 
the  above-mentioned  basis. 

The  formulas  of  Wm.  Kent  applied  to  the  determination  of  the  chimney  area, 
horse-power  and  height  are  based  upon  the  following  assumptions: 

1.  The  draft  power  of  the  chimney  varies  as  the  square  root  of  the  height. 

2.  The  retardation  due  to  friction  between  the  ascending  smoke  stream  and 
the  chimney  walls  is  taken  care  of  on  the  assumption  that  there  is  a  layer  of  gas 
two  inches  thick  against  the  walls  which  has  zero  velocity. 

3.  The  power  varies  directly  as  the  effective  area. 


So  H.  P.  =3.33  Evil,  H  =  f  °'3 

W  here  A  =  total  area  in  square  feet, 
horse-power,  II  =  height  in  feet. 

The  coefficient  0.6  may  be  used  for 
the  case  of  the  latter  the  diameter  of  the 

From  these  formulas  Tables  6,  7  and 
ne\  s,  w  ere  computed. 


P-Y  E-  —  —  R 

\  II 

F  =effecti\  e  area  in 


,  E  =  A-0.6vA 
square  feet,  H.  P.  = 


both  square  and  round  chimneys,  and  in 
actual  section. 

8.  giving  the  boiler  horse-power  of  chim- 


TABLE 6 

SIZES  OF  CHIMNEYS  FOR  STEAM  BOILERS 
Calculated  by  Mr.  W  in.  R.  Kent,  From  His  Formulae  Given  on  Page  51,  Assuming 
5  Lbs.  Coal  Required  Per  Boiler  Horse-Power  Hour 


Diarn.. 

Inches 

Area, 

Sq.  Ft. 

Effect. 

Area 

HE 

IGHT  OF  CHIMNEY 

Equiv. 

Square 

Chimney 

Side, 

Inches 

50'  ,  60' 

70' 

80' 

90' 

100' 

110' 

125' 

150' 

175' 

200' 

225' 

250' 

275' 

.300' 

COMMERCIAL  HORSE  POWER  OK 

BOILE 

RS 

30 

4.91 

3.58 

84  |  92 

100 

107 

113 

119 

27 

33 

5  94 

4  48 

1  1 5 

125 

1 33 

141 

149 

30 

36 

7  07 

141 

152 

163 

173 

182 

191 

204 

32 

39 

8  30 

183 

196 

208 

219 

229 

245 

35 

42 

9  62 

7.76 

216 

231 

245 

258 

271 

289 

316 

38 

48 

12  57 

10  44 

311 

330 

348 

365 

389 

126 

43 

54 

15  90 

13.51 

127 

449 

472 

503 

595 

48 

60 

19  64 

16  98 

565 

593 

632 

692 

748 

54 

23.76 

20 . 83 

694 

728 

776 

849 

918 

981 

59 

28  27 

25  08 

835 

876 

934 

1023 

1105 

1181 

1253 

64 

78 

33.18 

29.73 

10.38 

1107 

1212 

1.310 

1400 

1485 

1 565 

. 

70 

84 

38  48 

34 . 76 

121 1 

1294 

1418 

15.31 

16.77 

17.36 

1830 

1919 

2005 

75 

90 

44  18 

40.19 

1496 

16.39 

1770 

189.3 

2008 

21  16 

2219 

23 1 8 

80 

96 

50.27 

46  01 

1713 

1876 

2027 

2167 

2298 

242.3 

2511 

2654 

86 

102 

56 . 75 

52.23 

1944 

21.70 

2300 

2459 

2609 

2750 

2884 

.7012 

91 

108 

63 . 62 

58.83 

2190 

2392 

2592 

2770 

2939 

.3098 

.3249 

.7.39.7 

96 

111 

70  88 

65  83 

2685 

2900 

3100 

.3288 

.3466 

3635 

3797 

101 

120 

78.54 

73.22 

2986 

3226 

.3448 

.3657 

.7855 

4043 

4223 

107 

132 

95  03 

89  18 

36.37 

.3929 

4200 

4455 

4696 

4925 

5144 

117 

144 

113.10 

106.72 

4352 

4701 

5026 

53.31 

5618 

589.3 

6155 

128 

132  72 

125  82 

5542 

5925 

662 1 

6948 

7256 

138 

168 

153.94 

146.50 

6454 

6899 

7.318 

7713 

8090 

8449 

149 

180 

176.71 

168.74 

74.33 

7916 

8429 

8884 

9.318 

97.32 

160 

192 

201  06 

192.56 

9068 

9619 

101.38 

10633 

1  1 105 

170 

204 

226.98 

217  94 

1 0263 

1 0885 

1  1  175 

1 2035 

1 2569 

181 

216 

254  47 

244  90 

1 2233 

L289 1 

135  ’  5 

14123 

191 

228 

283  53 

273 . 53 

1  1396 

1 5099 

1 5768 

202 

240 

31  1  16 

303.53 

16761 

1 7505 

213 

51 


T\BLE  7 


SIZES  OF  CI11\INE\  S  FOR  STEWI  ROIEERS 


Calculated  !• 

rom  M 

r.  \\  m 

R.  Kent’s 'Table,  Assuming  1 

00  Lbs. 

Coal  R 

■quired 

’er  Boil 

er  Horse-Power 

1  lour 

I  )iam., 

Area 

(A). 

H EI (BIT  OF 

CHIMNEY 

Equi  v. 
Sq.  Chi  in. 

50' 

60' 

70' 

80' 

90' 

100' 

1 10' 

125' 

150' 

175' 

200' 

225' 

250' 

300' 

S(|.  1 1. 

HORSE-POWER— 3.25  A 

V  ii 

Side,  In. 

18 

1.77 

42 

46 

19 

52 

1 6" 

21 

2.41 

55 

02 

65 

68 

19" 

24 

3.14 

72 

78 

85 

91 

98 

22' 

27 

3  98 

91 

mi 

tor 

1 1 1 

124 

24' 

30 

4.91 

1 14 

124 

133 

143 

1 53 

159 

27' 

33 

5.94 

1  19 

163 

172 

182 

192 

202 

30' 

36 

7 . 07 

179 

192 

205 

218 

228 

211 

257 

32' 

39 

8  30 

224 

241 

257 

270 

283 

302 

35' 

42 

9.62 

263 

282 

296 

312 

332 

351 

390 

39' 

48 

12  57 

304 

387 

no 

129 

458 

510 

43' 

54 

15.90 

491 

517 

543 

579 

647 

683 

48' 

60 

19.64 

605 

637 

669 

715 

797 

845 

54' 

66 

23  70 

774 

809 

865 

965 

1021 

1092 

59' 

72 

28 . 27 

920 

962 

1051 

1  l  17 

1215 

1300 

1378 

61' 

78 

33  18 

1 1  3 1 

1 206 

1 349 

1459 

1524 

1  0  1  9 

1  706 

70' 

81 

38  48 

1310 

1  till 

1 563 

1654 

1768 

1 875 

1 976 

2H>5 

i  5' 

90 

44  18 

1609 

1  794 

1  898 

203 1 

2155 

2269 

2186 

80' 

96 

50  27 

1830 

2041 

2101 

2311 

245 1 

2584 

283 1 

86' 

102 

56  75 

2067 

2304 

2434 

2607 

2766 

2915 

3 1 95 

91' 

108 

63  62 

2314 

2584 

2734 

2925 

3101 

3269 

3578 

96' 

114 

70  88 

2879 

3045 

3257 

3455 

30  43 

3901 

101' 

120 

78.54 

3191 

3374 

361 1 

3829 

4037 

4420 

107' 

132 

95 . 03 

3861 

4082 

4368 

46.31 

1882 

5350 

117" 

144 

113  11) 

4596 

4859 

5200 

5515 

58 1  1 

6367 

128" 

The  formulas  and  tables  of  Win.  Kent  just  discussed  are  based  in  part  upon 
the  results  obtained  in  a  large  number  of  power  plants. 

For  comparatively  small  installations  operated  at  moderate  ratings,  they  are 
sufficiently  accurate  for  layouts  and  estimates. 

Mr.  Kent  himself  states  that  the  tables  give  the  boiler  horse-power  the  chimney 
will  serve  only  when  the  draft  losses  are  not  excessive. 

To  determine  the  required  height,  the  loss  of  draft  must  be  ascertained,  due 
to  all  causes,  from  the  ashpit  to  the  point  where  the  flue  enters  the  chimney. 

TABLE  8 

SIZES  OF  CHIMNEYS  FOR  STEAM  BOILERS 

Calculated  From  Mr.  Wm.  IL  Kent’s  Table,  Assuming  3.86  Lbs.  Coal  Required  Per  Boiler  Horse-Power  Hour 


Diana., 

Inches 

Area, 

Sq.  Ft. 

HEIGHT  OF  CHIMNEY 

Equiv. 

Square 

Chimney 

Side, 

Inches 

Effect. 

Area 

50' 

60' 

70' 

80' 

90' 

100' 

110' 

125' 

150' 

175' 

200' 

225' 

250' 

275' 

300' 

COMMERCIAL  HORSE-POWER  OF 

BOILERS 

30 

4.91 

3 . 58 

109 

119 

130 

1 39 

146 

154 

27 

33 

5 . 94 

4.48 

1 49 

162 

172 

183 

193 

202 

30 

36 

7.07 

5 . 47 

1 83 

197 

211 

224 

236 

217 

264 

32 

39 

8  30 

6 . 57 

237 

254 

269 

28 1 

296 

317 

35 

42 

9.62 

7.76 

280 

300 

317 

334 

351 

374 

409 

38 

48 

12.57 

10.44 

403 

427 

150 

472 

50 1 

43 

54 

15.90 

13.51 

553 

582 

01  1 

65 1 

715 

770 

18 

60 

19.64 

16.98 

695 

732 

768 

820 

896 

97(1 

54 

66 

23 . 76 

20.83 

900 

9 13 

I  005 

1  099 

1188 

1 270 

59 

28.27 

25 . 08 

1080 

11.35 

1209 

1325 

1  131) 

1 530 

1 623 

61 

78 

3.3.  18 

29 . 73 

1342 

1433 

1570 

1698 

1811 

L924 

2025 

70 

81 

38.48 

34.76 

1571 

1678 

1 835 

1984 

2120 

2246 

2370 

2  is  i 

2600 

75 

90 

44.18 

40  1 9 

1940 

2120 

2292 

2151 

2600 

2710 

2870 

3000 

80 

96 

50.27 

46  01 

2220 

2  130 

2625 

2805 

2975 

3 1  10 

3300 

3  1 10 

86 

102 

52  23 

2520 

2760 

2980 

3180 

3380 

3561 

3710 

3900 

91 

108 

63 . 02 

58  83 

2810 

3 1 00 

3360 

3585 

3800 

4010 

1210 

1  100 

96 

114 

70.88 

65 . 83 

3  180 

3760 

4012 

4260 

1  190 

4710 

1920 

101 

120 

78  54 

73 . 22 

3870 

1220 

1  160 

1 730 

1990 

5240 

5 180 

107 

132 

95  03 

89.18 

ITOil 

5090 

6  140 

5775 

6075 

6  180 

6650 

117 

144 

1  13  10 

100.72 

5650 

6 1 00 

6520 

6900 

7280 

7625 

7 1 » 7 

128 

156 

1.32.73 

125.82 

7170 

7675 

8110 

8590 

9000 

9  100 

138 

108 

153.94 

1  to  50 

8360 

8925 

9480 

1 1)000 

In  17ii 

l  0920 

1  19 

180 

176.71 

108.71 

9630 

10280 

10920 

1 1 500 

12060 

1 2600 

160 

192 

201.06 

192.56 

117  10 

12450 

13130 

1 3790 

1  1 100 

170 

201 

226  98 

217.94 

13290 

1  l  LOO 

1  1850 

1  '.(.ini 

16280 

131 

216 

254.47 

24  l . 90 

1 5850 

L6700 

1 7500 

1 8  100 

191 

228 

283  53 

273  53 

18650 

L9550 

20  100 

202 

240 

31 1  16 

303 . 53 

21700 

22650 

213 

The  maximum  available  draft  required  for  a  given  installation  may  be  expressed 
by  the  formula 


55 


MAD  =  LG+LI +LB  +LF  +  LT  +LE,  L,  etc. 

W  here  MAD  =  maximum  available  draft  required. 

LG  =the  loss  through  the  fuel  bed  necessary  to  produce  the  required 
rate  of  combustion. 

L  I  =  the  loss  to  provide  furnace  vacuum,  etc. 

LB=the  loss  through  the  boiler  at  the  rating  assumed  as  the 
maximum  required. 

LF=the  loss  through  t lie  Hue. 

LT  =the  loss  due  to  the  turns  or  bends  in  the  path  of  the  smoke 
stream  after  leaving  the  boiler. 

LE  =  t lie  loss  through  the  economizer  if  used. 

L,  etc.  =the  loss  through  any  other  apparatus  in  the  path  of  the  gases* 
such  as  settling  chambers,  baffles,  super-heaters,  etc. 

The  draft  loss  in  the  flue  or  breeching  depends  upon  its  length,  its  cross  section, 
the  material  it  is  built  of  and  the  number  of  bends.  The  smoother  the  inside  of 
the  flue,  the  straighter  it  is,  the  nearer  it  approaches  to  a  circle  in  cross  section, 
the  less  the  loss  at  a  given  gas  velocity.  Sharp  right  angle  bends,  sudden  changes 
in  area  or  shape  of  section,  are  to  be  avoided  and  all  changes  of  direction  made 
easily.  If  the  chimney  can  lie  placed  in  the  geographical  center  of  the  batteries 
of  boilers,  minimum  lengths  of  flues  are  generally  obtained. 

As  a  general  rule  in  steel  Hues  of  circular  section  there  will  be  a  loss  of  0.10  of 
an  inch  per  100  feet  of  length  with  normal  gas  velocities.  Each  right  angle  bend 
represents  a  loss  of  0.05  of  an  inch.  If  the  flues  are  square  or  rectangular  there 
will  be  an  average  additional  loss  ranging  up  to  25%.  The  loss  increases  as  the 
ratio  of  height  to  width  increases.  If  the  flues  are  built  of  masonry  there  will  be 
a  further  loss  unless  the  walls  are  smooth. 

Hdie  loss  of  draft  through  the  boiler  itself,  i.  e.,  from  the  top  of  the  fire  to  the 
point  where  the  gases  leave  the  boiler  and  enter  the  flues,  depends  upon  a  number 
of  factors  and  varies  widely.  The  factors  are — the  size  and  type,  the  number  of 
tubes  and  the  way  they  are  set,  the  type  of  grate,  the  method  of  baffling,  and  rating 
at  which  the  boilers  are  operated.  This  loss  may  vary  from  0.15"  to  0.25"  at  rating, 
to  0.80"  or  0.85"  for  a  maximum  of  250%  or  more  rating.  It  is  advisable  for  the 
engineer  to  cooperate  with  the  boiler  manufacturer  in  determining  the  loss  of 
draft  to  be  assumed  through  the  particular  type  and  setting  of  boiler  at  maximum 
rating  required. 

With  natural  draft  stokers  and  hand  fired  furnaces  there  is  an  additional  loss 
through  the  fuel  bed,  dependent  upon  its  thickness,  the  kind  of  fuel  and  the  type 
of  grate.  There  is  a  certain  draft  over  the  fuel  bed  that  will  give  the  best  results 
for  every  combustion  rate  and  kind  of  fuel.  Again,  it  is  advisable  for  the  engineer 
to  cooperate  with  the  boiler  and  stoker  manufacturer  in  determining  the  loss  of 
draft  to  be  assumed  through  the  fuel  in  order  to  produce  the  best  results  from  a 
specific  fuel  and  type  of  boiler  fired  at  the  desired  ratings. 


56 


With  Ihe  forced  draft  type  of  stoker  the  re([iiireineirt  is  somewhat  different, 
for  Ihe  reason  that  the  air  is  forced  through  the  fuel  bed  by  fans,  relieving  the 
chimney  of  this  duty. 

It  is  considered  good  practice  to  allow  0.05  inch  to  0.15  inch  draft  over  the 
lire  in  all  forced  draft  installations  to  prevent  Ihe  formation  of  positive  pressures  in 
Ihe  furnace.  If  this  allowance  is  not  made,  there  is  a  possibility  of  overheating 
the  furnaces  and  fronts;  also  there  is  the  possibility  of  objectionable  gases  being 
forced  out  into  the  boiler  room. 

If  economizers  are  used  betw  een  the  boilers  and  chimney  there  is  an  additional 
loss  in  draft,  due  to  friction  through  the  economizer. 

This  friction  loss  varies  within  wide  limits,  depending  upon  the  type  of  econ¬ 
omizer,  the  number  of  tubes,  the  length  and  the  velocity  of  the  gases  passing 
between  the  tubes.  The  efficiency  of  the  economizer  is  dependent  upon  the  gas 
velocity.  The  economizer  reduces  the  temperature  of  the  flue  gases.  This 
reduces  materially  the  available  draft,  or  in  other  words  affects  the  required  height 
of  chimney. 

With  lowr  stack  temperatures  and  economizers,  to  depend  upon  natural  draft 
alone  would  require  a  ridiculously  high  chimney,  especially  with  a  fine  grade  of 
coal  and  boilers  operated  at  high  ratings.  In  this  case  the  best  modern  practice  in 
isolated  plants,  w  here  overloads  from  200%  to  250%  or  more  are  contemplated,  is 
to  provide  a  chimney  of  ample  height  and  diameter  to  operate  the  boilers  when  the 
economizers  are  cut  out;  then  to  provide  induced  draft  fans  to  furnish  the  additional 
draft  needed  with  the  economizers  in  service. 

Mistakes  have  been  made  in  the  past  by  trying  to  reduce  the  chimney 
heights  in  such  cases.  This  resulted  in  the  sluggish  movement  of  gases  through  the 
boilers  and  economizers,  with  inefficient  and  incomplete  burning  of  the  coal  and 
disappointing  results  as  to  capacity. 

Therefore,  to  meet  heavy  peak  loads  with  economizers  the  chimney  should  be 
of  ample  height  supplemented  with  induced  draft  fans  to  overcome  all  Ihe  pre¬ 
viously  cited  losses,  so  that  there  is  a  constant  flow  of  gases  from  ashpit  to  chimney. 

W  here  many  boilers  are  connected  to  one  chimney  the  temperature  and 
quantity  of'  flue  gas  depends  upon  the  number  of  boilers  in  service  and  the  ratings 
at  which  they  are  operated.  Therefore  the  available  draft  varies. 

Accordingly  w  hen  a  few  boilers  are  operated  at  high  ratings  to  carry  t  he  over¬ 
load  the  flue  gas  temperatures  are  higher  and  the  available  draft  is  increased.  On 
the  other  hand,  operating  a  majority  of  the  boilers  at  low  ratings  decreases  the 
temperatures  and  the  draft  falls  off.  The  varied  conditions  expected  should  be 
studied  to  determine  the  proper  size  of  chimney  and  whether  more  than  one 
chimney  should  be  installed. 

The  economy  and  efficiency  of  operation  during  the  life  of  the  plant,  rather 
than  first  cost,  should  be  given  due  weight  in  making  this  decision.  It  may  be  that 
property  limits  will  restrict  the  available  space  so  that  there  is  only  one  solution  of 
the  problem. 


Radial  1  trick  chimneys  ranging  from  275  feet  to  350  feet  high,  with  diameters 
in  proportion,  are  economically  and  successfully  operated  in  many  large  power 
plants. 

It  will  he  noted  we  have  assumed  an  outside  air  temperature  of  60°  F.  in 
making  the  draft  calculations.  In  northern  climates,  for  months,  the  temperatures 
are  often  below  freezing  and  there  are  periods  when  the  temperatures  are  far  below 
0°  F.,  while  in  summer  the  temperature  may  be  above  90°  F.  The  available  draft  is 
greater  in  winter  and  may  vary  75%  throughout  the  year.  In  selecting  a  chimney 
size  due  allowance  should  be  made  for  the  most  adverse  atmospheric  conditions. 
These  occur  when  the  outside  air  temperatures  are  highest  and  the  barometer 
low  est. 

When  designing  a  chimney  to  serve  a  heating  plant  located  in  northern  lati¬ 
tudes  it  is  customary  to  assume  that  the  temperature  of  the  outside  air  will  be 
somewhat  less  than  60°  F.  However,  it  is  wise  to  be  conservative  in  reducing 
stack  heights  and  to  recommend  ample  dimensions  w  here  there  is  any  doubt.  The 
boiler  cannot  lie  operated  efficiently  or  at  high  ratings  unless  the  chimney  is 
properly  proportioned.  Many  power  plant  ow  ners  have  saved  thousands  of  dollars 
and  avoided  embarrassment  by  having  ample  stack  height  and  capacity.  It  is 
impossible  to  predict  the  quality  of  coal  which  can  be  secured  at  all  times  or  when 
a  stoker  or  boiler  w  ill  require  repairs  or  overhauling.  There  is  a  reserve  in  every 
unit  of  a  well-designed  power  plant,  its  stokers,  its  boilers,  its  pumps,  its  engines  or 
turbines,  and  that  principle  should  be  carried  straight  through  to  the  chimney.  If 
not,  the  reserves  back  of  the  chimney  will  fall  short  of  their  purpose. 

Each  installation  is  a  study  of  ils  own.  The  important  problem  is  the  deter¬ 
mination  of  the  available  draft  required  at  the  point  where  the  flue  enters  the 
chimney,  giving  careful  consideration  to  the  draft  losses  through  all  the  equipment. 
Practical  experience,  good  judgment  and  a  study  of  the  equipment  are  required  for 
each  installation  and  no  one  can  lay  down  fixed  rules  to  apply  to  all  cases. 

The  diameter  of  the  chimney  is  determined  on  a  gas  basis  as  previously 
described. 

CHIMNEYS  IN  CONNECTION  WITH  STEAM  BOILER 
PLANTS  BURNING  OIL 

The  sizes  of  chimney  to  be  used  where  fuel  oil  is  burned  are  determined  in  the 
same  w  ay  as  w  hen  coal  is  used  as  fuel. 

For  several  reasons  calculations  will  result  in  a  chimney  of  less  height  and 
smaller  diameter. 

There  is  no  fuel  bed  loss;  in  fact  some  types  of  burners  have  a  certain  forced 
draft  action. 

Less  weight  of  air  per  horse-pow  er  is  required;  consequently,  the  pressure  drop 
through  the  boiler  and  fines  is  less  than  when  coal  is  burned.  Some  reduction  in 


53 


the  height  of  the  chimney  is,  therefore,  permissible,  but  it  should  be  borne  in  mind 
that  the  flue  gas  temperatures  are  lower  when  oil  is  burned.  I  bus  reducing  the 
available  draft. 

The  height  should  be  sufficient  to  furnish  the  draft  required  at  peak  loads  and 
no  more.  This  is  much  more  important  in  the  burning  of  oil  than  in  the  burning 
of  coal.  In  the  lat  ter  case  there  is  little  or  no  danger  of  too  much  draft. 

In  the  former  great  loss  in  economy  may  result  from  excessive  draft  during  the 
periods  of  light  load.  This  is  especially  true  in  plant  operating  a\  i 1 1 1  a  fluctuating 
boiler  load.  Automatic  control  does  much  to  eliminate  this  evil.  It  permits  the 
proper  height  to  be  used  without  undue  losses.  This  is  as  it  should  be.  Always 
determine  the  height  of  chimney  for  maximum  boiler  requirements. 

Several  authorities  state  that  good  results  are  obtained  by  reducing  the  area 
from  35  to  45%  below  that  required  for  coal  burning.  This  is  merely  an  arbitrary 
assumption.  Such  a  method  is  not  recommended.  The  diameter  is  dependent 
entirely  upon  the  volume  of  gases  to  be  moved  at  a  given  velocity.  This  volume  is 
dependent  upon  the  calorific  value,  the  composition,  and  amount  of  the  oil  burned, 
together  with  the  percentage  of  excess  air. 

Some  boiler  manufacturers  give  tables  of  chimney  sizes  suitable  for  various 
oil-fired  boiler  plants.  They  are  useful  only  as  a  check  after  the  size  has  been 
determined  by  method  previously  described. 

In  proportioning  chimneys  for  oil-fired  furnaces,  consideration  should  be  given 
to  the  possibility  of  having  to  turn  to  coal  for  fuel,  due  to  scarcity  and  high  price 
of  oil. 

CHIMNEYS  IN  CONNECTION  WITH  STEAM  BOILER  PLANTS 
BURNING  WOOD  REFUSE  AND  OTHER 
BY-PRODUCTS  FUELS 

The  determination  of  sizes  of  chimney  used  for  steam  boiler  plants  with  these 
fuels  is  more  a  matter  of  experience  than  of  calculation,  for  the  data  is  very  meager 
concerning  the  performances  of  boilers  burning  them.  This  applies  particularly 
to  the  determination  of  the  diameter. 

The  height,  however,  admits  of  a  more  exact  determination  by  calculating  the 
pressure  drops.  However,  it  should  be  borne  in  mind  that  with  wood  refuse  these 
are  likely  to  be  considerably  higher  than  they  are  in  t  he  case  of  coal  or  oil  on  account 
of  the  abnormal  quantities  of  excess  air  passing.  Also,  as  is  always  the  case  w  hen 
the  percentage  of  excess  air  is  high,  the  flue  gas  temperatures  are  much  higher  than 
they  are  with  coal  or  oil  and  this  should  be  borne  in  mind  when  making  draft 
calculations. 

The  loss  through  the  lire  is  generally  less  with  by-product  fuels  than  it  is  with 
coal,  because  most  of  the  combustion  is  surface  combustion.  However,  the 
determination  is  largely  a  matter  of  experience. 


Example  111.  Determine  the  height  and  diameter  of  a  circular  masonry 
chimney  for  the  following  conditions: 

\\  ater  tube  boilers,  hand  fired,  builder's  rating  1500  H.  P.,  burning  Virginia 
semi-bituminous  coal,  calorific  value  13.000  B.  t.  u.,  boiler  rated  at  10  sq.  ft.  heating 
surface,  ratio  of  heating  surface  to  grate  surface  50  to  1,  length  of  circular  steel 
breeching  40  feet,  2  right-angle  bends,  outside  air  60°  F.,  average  internal  stack 
temperatures  560°  F..  location  sea  level,  boilers  operated  at  a  maximum  of  150% 
of  rating. 

W  ith  this  equipment,  a  combined  efliciencx  of  65%  may  reasonably  be  assumed, 
f  nit  of  evaporation  =972  B.  t.  u. 

One  boiler  H.  P.  is  equivalent  to  34.5x972=33,534  B.  t.  u. 

33  53  j 

Pounds  of  coal  burned  per  boiler  horse  power  hour  - !  =3.97 

1  1  13,000x0.65 

Boiler  H.  P.  developed  1500x1.5  =2250 

1500x10 

Square  leet  ol  grate  surface  - — - =  300 

1  &  50 

Total  pounds  coal  burned  per  hour  2250x3.97  =8933 

Pounds  of  coal  burned  per  square  foot  grate  surface  =29.78 

Summing  the  draft  losses  up,  we  have 

Loss  through  lires  and  grates . 0.40" 

Loss  through  boiler,  depending  upon  type  and  setting . 0.45" 

Loss  in  steel  flue  circular  section  70'—  0.10  per  100' . 0.07" 

Loss  in  two  right  angle  turns . 0.10" 

Total . X0277 

,  1.02 

1  heoretical  draft  required  — _ =1.275  inches 

1  .80 

.  ...  /  7.64  7.94\ 

H  =  187  feet. 

To  determine  the  diameter.  Our  assumption  was  that  Virginia  semi- 
bituminous  coal  was  to  be  burned.  Pounds  air  required  per  10,000  B.  t.u.  (U.  S. 
Bureau  of  Mines)  =7.6. 

Pounds  of  air  per  pound  of  coal  =  7.6  |  ^ — —0=9.88. 

Assume  an  allowance  for  excess  air  of  90%  to  provide  against  possible  holes 


60 


in  fire,  defective  sellings,  leakage  and  adverse  conditions,  giving  19  pounds  of  air 
per  pound  of  coal. 

The  total  weight  of  coal  burned  per  hour  =8933  pounds. 

The  total  weight  of  flue  gas  per  hour  =  20.0  X  8933  =  178,660. 

Weight  of  Hue  gas  per  second  =19.5  pounds. 

Density  of  gases  at  580°  F.  (see  Fig.  No.  2)  =0.0410  pounds  per  cubic  foot. 

49.5 

Total  volume  ol  flue  gases  per  second  =  —  =  1208  cubic  feet. 

Assume  that  the  economical  velocity  is  22.5  feet  per  second. 

1208 

I  he  minimum  effective  area  required  =  =53.7  square  feet. 

22.o 

The  minimum  diameter  required  =8'  3". 

On  the  assumed  premises  select  a  chimney  187'  0"x8'  3". 


00  200  300  400  500  600  700  800  900 

Temperature  Deg.  Fahr. 

Fig.  32 

Weight  of  flue  gas  per  cubic  foot  at  various  temperatures 

Referring  to  table  No.  8,  which  is  based  upon  the  assumption  that  3.86  pounds 
of  coal  are  burned  per  boiler  horse-power  hour,  it  is  seen  that  there  are  several 
chimney  sizes  given  as  capable  of  serving  1500  rated  boiler  horse-power. 

If  any  of  the  chimney  sizes  were  selected  which  had  a  height  appreciably  less 
than  187  feet  it  would  be  impossible  to  operate  the  boiler  at  150%  of  rating, 
and  if  the  height  were  appreciably  more  than  187  feet  the  chimney  would  not  be 
of  the  most  economical  dimensions  for  this  particular  case. 

It  is,  therefore,  evident  that  the  only  safe  method  to  employ  is  to  compute 
the  height  and  diameter  in  accordance  with  the  principles  laid  down  in  the  sample 
problems  heretofore  given  and  to  ignore  all  tables  and  formulas. 

Example  IV.  Assume  the  same  conditions  as  before  except  that  the  boilers 
are  operated  at  200%  of  rating  with  forced  draft  stokers.  Determine  the  height 
and  diameter  of  the  required  chimney. 


61 


The  draft  required  through  the  fuel  bed  is  taken  care  of  by  the  fans  with  forced 
draft  stokers. 

The  volume  of  gas  formed  per  second  will  increase  as  the  horse-power  developed 


increases.  Consequently  the  draft  loss  through  the  boiler  increases. 

Summing  up  the  draft  losses  we  have: 

Initial  draft  over  fires  for  furnace,  vacuum,  etc .  0.10 

Loss  through  boiler  at  200%  rating,  depending  upon  type  of  boiler 

settings,  baffling,  etc .  0.70 

Loss  through  flue  (as  before) .  0.07 

Loss  in  two  right  angle  bends .  0.10 

Total .  0.97 


Theoretical  draft  required 


.97 

.80 


1.21  inches. 


\t  200%  of  rating  assume  the  average  temperature  in  the  chimney  to  be 
580°  F.  with  outside  air  60°  F. 


1.21 


11 


11  =  173  feet. 


An  assumption  of  a  combined  efficiency  of  70%  is  reasonable. 


Pounds  of  coal  burned  per  boiler  11.  P.  per  hour  = 

1  1  13.000X.70 


=  3.68. 


Boiler  H.  P.  developed  =  1500x2  =3000. 

Pounds  of  coal  burned  per  hour  =  3000x3.68  =  1 1,0 10. 

With  forced  draft  stokers  it  is  usualh  safe  to  assume  18  pounds  of  air  per 
pound  of  coal  burned. 

Total  weight  of  flue  gas  per  hour  =  19x11.0 10  =  209,760  pounds. 

Weight  of  flue  gas  per  second  =58.3  pounds. 

Density  of  gases  at  580°  F.  (see  Fig.  32)  =.010. 


Total  volume  of  gases  per  second 


58.3 

.04 


=  1157 


5  cubic  feet. 


Assume  that  the  economical  velocity  is  21  feet  per  second. 


rhe  minimum  effective  area  required 


1457.5 

21 


=  60.8  square  feet. 


The  minimum  diameter  required  =8'  10". 

On  the  assumed  premises  select  a  chimney  173' X 8'  10". 

The  height  is  less,  as  it  is  not  necessary  for  the  chimney  to  furnish  the  draft 
for  drawing  the  air  through  the  fuel  bed. 

The  draft  loss  through  the  boiler  plus  the  draft  loss  for  furnace  vacuum  is  less 
than  the  loss  was  through  the  boiler  and  grates  in  the  case  of  hand  firing. 


62 


The  height  of  chimney  calculated  in  the  examples  is  the  net  height,  or  that 
measured  above  the  boiler  damper.  If  the  breeching  is  level,  the  height  will,  of 
course,  be  measured  from  t  lie  point  where  the  breeching  enters  the  chimney. 
The  total  height  of  the  chimney  will  be  the  net  height  plus  the  distance  from  the 
datum  point  to  the  top  of  the  chimney  foundation. 

Chapter  IV 

CALCULATION  OF  STRESSES  IN  CHIMNEYS 

We  have  set  forth  in  the  previous  chapter  the  principles  for  determining  the 
height  and  diameter  of  a  chimney  for  a  specific  installat ion.  The  laws  of  Mechanics 
determine  the  structural  design,  due  consideration  being  given  to  securing  the 
most  economical  stable  structure  that  will  resist  the  action  of  the  wind,  weather 
and  internal  gases. 

Many  engineers  and  architects  prefer  to  leave  the  design  of  the  chimney  to 
the  chimney  company.  For  the  benefit  of  those  who  desire  to  prepare  their  own 
plans  and  specifications  the  following  is  a  brief  resume  of  the  principles  involved 
and  methods  employed. 

Let  us  consider  the  chimney  shown  in  Fig.  33,  with  no  wind 
blowing.  In  any  horizontal  section  of  the  chimney  the  dead 
w  eight  of  the  superincumbent  portion  is  uniformly  distributed 
over  the  bearing  walls  and  therefore  the  pressure  on  each 
horizontal  unit  of  area  in  the  section  is  the  same,  that  is  to  say 
the  “fiber  stress  "  in  the  brickwork  is  a  uniform  compression. 

\\  hen  a  wind  of  a  given  velocity  blows  against  the  chimney  it 
exerts  a  certain  force  (pressure)  on  the  windward  side.  Assume 
for  the  present  that  the  intensity  of  this  force  is  uniform  from 
the  top  to  the  bottom.  The  force  created  by  the  wind  tends 
to  push  the  shaft  over  iu  the  direction  of  the  wind.  As  a 
consequence,  the  intensity  of  the  compression  on  any  hori¬ 
zontal  section  due  to  the  dead  weight  of  the  superincumbent 
portion  is  increased  on  the  lee  side  and  decreased  on  the 
w  indward  side.  The  decrease  may  be  larger  than  the  pre¬ 
existent  intensity,  in  which  case  the  net  result  will  be  a  tensile 
stress. 

We  then  have  a  structure  supported  at  one  end.  acted 
upon  byr  two  forces:  one,  the  dead  weight  applied  along  its 
longitudinal  axis,  the  other,  the  wind  load  applied  perpen¬ 
dicularly  to  that  axis.  From  the  above  description  it  is 
evident  that  the  well-known  cantilever  beam  formulas  apply 
provided  the  material  is  not  stressed  beyond  its  elastic  limit. 

Notation. — In  the  following  let 

A  =  area  of  horizontal  section  under  consideration  in 
square  feet; 


63 


G=  weight  of  brickwork  of  superincumbent  portion  of  chimney  in  tons; 
W=wind  pressure  on  that  portion  in  tons; 

L  =  distance  from  section  to  resultant  of  wind  pressure  in  feet; 

M  =  bending  moment  at  the  section  in  foot  tons; 

S'  =  intensity  of  stress  at  lee  side  in  tons  per  square  foot; 

S"  =  intensity  of  stress  at  windward  side  in  tons  per  square  foot; 

P=  intensity  of  wind  pressure  in  pounds  per  square  foot  of  projected  area; 
a  =  distance  from  the  center  of  the  section  to  where  the  resultant  of  the 
weight  and  wind  pressure  cuts  the  section,  “eccentric  distance”; 

1  =  second  moment  (moment  of  inertia)  of  area  of  section  about  an  axis 
through  the  center  and  normal  to  the  direction  of  the  wind. 

In  the  case  of  a  circular  chimney  let 

Di=outside  diameter  at  top  of  chimney  in  feet; 

1)  =  outside  diameter  at  section  in  feet; 

R  =  outside  radius  at  section  in  feet; 
r=  inside  radius  at  section  in  feet; 

II  =  height  of  superincumbent  section  in  feet;  then 


D  +  Di  PH 

2  2000 

(1) 

D  +2Di  H 

D+Di  3 

(2) 

M  =  \\  L  =  bending  moment.  (3) 

Applying  the  cantilever  beam  formulae,  we  obtain: 


Also 


S'  = 


S"  = 

w 

g” 


G  MR 

A+^~ 

(4) 

G  MR 

(5) 

A  1 

a  M 

L  °r  ”  =  G 

(6) 

If  we  assign  values  for  allowable  tension  and  compression  we  can  proceed 
with  the  structural  design.  The  strength  of  masonry  in  tension  is  low  compared 
with  its  strength  in  compression.  The  strength  in  tension  may  be  reduced  to 
almost  zero  through  poor  workmanship.  To  design  masonry  structures  other  than 
chimneys  without  tension  does  not  greatly  increase  the  total  cost,  and  specifications 
generally  do  not  permit  tension  in  such  masonry.  In  chimney  construction,  the 
cost  may  be  greatly  increased  by  designing  to  eliminate  all  tension.  We  will, 
therefore,  investigate  further  on  the  assumption  that  tension  may  safely  exist 
within  certain  limits  with  the  object  of  producing  the  most  economical  stable  design. 

The  “fiber  stress”  is  considered  to  be  a  uniformly  varying  stress  and  in  Ihe 
case  of  a  uniformly  varying  stress  we  learn  in  Mechanics  that: 


(1)  The  average  unit  stress  tor  any  portion  of  the  section  equals  the  unit 
stress  at  the  centroid  (center  of  gravity)  of  that  portion;  and 

(2)  The  total  force  is  equal  to  the  product  of  the  average  unit  stress  and  the 
area  of  the  portion  of  the  section;  or 

(3)  The  total  force  is  equal  to  the  product  of  the  lirst  moment  of  the  area  of 
the  portion  of  the  section  and  the  intensity  of  the  stressat  a  units  distance  from  the 
neutral  axis;  and 

(1)  Idie  resultant  of  the  stress  on  any  portion  of  the  section  has  its  point  of 
application  at  a  distance  from  the  neutral  axis  equal  to  the  ratio  of  the  second 
moment  of  the  portion  of  the  section  about  the  neutral  axis  to  the  first  moment 
of  the  portion  of  the  section  about  the  same  axis. 

The  following  principles  in  Mechanics  will  also  be  used: 

(5)  I  he  first  moment  of  an  area  about  an  axis  in  its  plane  is  equal  to  the 
product  of  the  area  and  the  distance  from  the  axis  to  the  centroid  of  the  area. 

(6)  ddie  second  moment  of  an  area  about  an  axis  in  its  plane  is  equal  to  the 
second  moment  of  the  area  about  a  parallel  axis  through  the  centroid  of  the  area 
increased  by  the  product  of  the  area  and  the  square  of  the  distance  between  the 
axes,  or  mathematically  expressed 

In  =  I<7  Tl2A  in  which 

l n  =  the  second  moment  of  the  area  about  the  required  axis. 

h/  =  the  second  moment  of  the  area  about  a  parallel  axis  through  the  centroid 
of  the  area; 

I  =the  distance  between  the  axes; 

A  =  area  under  consideration. 

Note.  —  The  mathematical  development  of  the  foregoing  principles  is  as 
follows: 


Let  \  = 
F  = 
/  = 
f- 

xF  = 
r/A  = 
X  = 

I  hen  in  = 


F  = 


area  under  consideration; 
total  force  acting  on  area; 

the  intensity  of  stress  at  a  unit's  distance  from  the  neutral  axis; 
average  unit  stress; 

the  distance  of  the  point  of  application  of  the  resultant  of  the  total  force  to  the  neutral  axis; 
differential  element  of  area  parallel  to  the  neutral  axis; 
distance  from  neutral  axis  to  differential  element  of  area; 
f  xdA  =  first  moment  of  area  about  neutral  axis; 

fxd A  _  B  =l 

A  A 
=ffxd\- 


.fxA 

A 


the  distance  of  the  centroid  of  the  area  from  the  neutral  axis; 
fxA=fm  (Principle  3). 

=fx  (Principle  1). 


By  comparing  F  =fx A  with  /  =f x  we  have  F  =/ A  (Principle  2). 

By  principle  of  moments 

Jr/ J  xdA  =/ j  x-dA  or 

_  I 

xF  =  —  (Principle  1), 
m 

where  I  =  j  x-dA,  the  second  moment  of  the  area  about  the  neutral  axis. 

c.  m 

Since  x  =  ir 

m  =  xA 


65 


W1  len  there  is  no  wind  blowing  (see  Fig.  34)  S'  =S"  =  S0  =  —  (7) 

Direction  ofWiad 


"f 

So 


25c 


Fig.  34. 

Stress  Distribution,  no 
wind  blowing — Neu¬ 
tral  Axis  at  Infinity. 


Fig.  35. 

Stress  Distribution, 
wind  blowing— Neu¬ 
tral  Axis  Tangent  to 
Section. 


Fig.  36. 

Stress  Distribution, 
wind  blowing — Neu¬ 
tral  Axis  through  Cen¬ 
ter  of  Section. 


G 


Suppose  now  that  t he  wind  pressure  is  such  that  S"  =0  and  S'  =2  —  =2S0  in 

which  case  the  neutral  axis  will  be  tangent  to  the  section  as  shown  in  Fig.  35.  Let 
the  value  of  a  under  these  conditions  be  designated  by  k,  then 
from  principles  4  and  6  we  have 

k  +  R  =  which  reduces  to  k  =  or  I  =kRA.  (8) 

o  •  f  c.\  M  1  ,  ,  ,  M 

By  equation  (6)  a  =  ~~  but  a  =k,  hence  k  =  —  . 

G  G 


Equating,  w  e  have 


I 


M 


RA  G 

The  value  of  k  obtained  under  these  conditions  will  be  referred  to  as  the  radius 
of  the  first  kern. 

If  now  we  place  M=aG  from  equation  (6)  and  I=kRA  from  equation  (8)  in 
equations  (4)  and  (5)  we  obtain 


(9) 

(10) 


66 


A  necessary  condition  to  prevent  overturning  is  that  the  resultant  of  the 
forces  of  the  wind  and  weight  must  fall  within  the  base;  therefore,  the  fact  that 
tension  exists  does  not  of  necessity  indicate  that  the  structure  is  unstable. 

On  the  above  principle  it  may  be  concluded  that  the  two  prime  requisites  for 
stability  in  a  chimney  are: 

(1)  The  resultant  must  fall  well  within  the  base.  It  is  arbitrarily  assumed 
that  the  resultant  must  fall  inside  an  area  such  that  there  is  no  tension  beyond  an 
axis  through  the  center  of  the  section  normal  to  the  wind,  that  is  to  say  that  the 
leeward  half  of  the  section  will  be  under  compression  and  that  there  will  be  no 
stress  on  the  w  indw  ard  half. 

(2)  The  maximum  compression  must  not  exceed  the  safe  limit  of  the  masonry. 

The  radius  of  the  area  described  under  requisite  (1)  we  will  refer  to  as  the 

radius  of  the  second  kern  and  designate  same  by  e. 

This  condition  is  shown  in  Fig.  36;  the  neutral  axis  passes  through  the  center 
of  the  section,  and  the  shaded  area  represents  the  area  under  compression. 

In  this  case  we  have,  applying  principle  4, 


m 

W  here  m  is  the  first  moment  of  the  shaded  area  about  the  neutral  axis  NN. 


..  .  ,  ^  S'm 

,  RG 

By  principle  3,  G  =  or  S 

comparing  with  equation  (11) 

/  _ 

Ill 

(12) 

2eRG 

(13) 

S' 

I 

substituting  I  =  kRA  from  equation 

(8)  in  equation 

(13) 

2e  G  e 

we  obtain  S'  =  — - =  2S0  —  • 

k  A  k 

(14) 

It  now  remains  to  show  howr  to  determine  the  value  of  a  for  positions  of  the 
neutral  axis  intermediate  to  those  shown  in  Figs.  35  and  36. 


Deflection  of  Resultant 
Fig.  37 

Value  of  Stress  for  Various  Positions  of  the  Resultant 


07 


In  Fig.  37  the  horizontal  axis  represents  the  various  positions  of  the  resultant  (in 


terms  of 


a 

\\ 


),  and 


the  vertical  axis  through  point  0  the  corresponding  unit  stresses. 


A\  hen  the  deflection  of  the  resultant  is  zero  there  is  no  wind  pressure  acting  and  the 
unit  compressive  strength  is  S0.  Plotting  this  value  the  point  F  is  obtained.  When 
the  deflection  of  the  resultant  is  equal  to  k,  the  radius  of  the  first  kern,  there  is  no 
tension  and  the  unit  compressive  stress  at  the  lee  side  is  2S0.  Plotting  this  value 
we  obtain  the  point  B.  The  straight  lines  FBC  and  FB'C'  may  now  be  drawn. 
The  line  FBC  will  then  represent  equation  (9),  the  unit  stress  on  the  lee  side,  and 
the  line  F'B'C'  equation  (10),  the  unit  stress  on  the  windward  side  after  replacing 
a 


a 

k 


by 


in  these  equations, 
k  1 

B 


For  values  of  a  >  k  or  when  the  distance  of  the  point  of  application  of  the 
resultant  from  the  center  is  greater  than  the  radius  of  the  first  kern,  S"  becomes 
negative,  indicating  tensile  stress  on  the  windward  side;  hence,  in  accordance  with 
our  previous  assumption  that  the  tensile  stress  no  longer  exists,  the  compressive 
stress  S'  must  be  increased  by  some  definite  amount  for  each  position  of  the 
resultant  beyond  the  first  kern.  This  assumption  will  produce  a  new  curve  start¬ 
ing  at  1:»  and  passing  through  II.  which  point  is  determined  by  equation  (14)  and 
which  will  lie  on  the  straight  line  OBH. 

The  equation  of  the  curve  BHQ  is  closely  approximated  by  the  equation 


between  k  and  e. 


by  means  of  which  S'"  can  be 


found 


for  values  of  a 


FOUNDATIONS 


In  making  calculations  for  the  maximum  compression  on  the  soil  in  foundation 
designs  it  is  assumed  that  the  compression  varies  in  accordance  with  the  straight 
line  law.  It  is  good  practice  to  provide  sufficient  weight  in  the  foundation  and 
chimney  to  eliminate  any  tendency  for  the  windward  toe  to  lift.  The  cantilever 
formula  is  then  applicable. 


Soil  pressure 


G 

A 


± 


M 

V 


where  G  =  total  dead  weight  above  bottom  of  foundation : 

A  =  area  of  bottom  of  foundation; 

V  =  section  modulus  of  bottom  of  foundation; 

M  =  bending  moment  at  the  foot  of  the  foundation. 

If  the  tension  in  the  outstanding  cantilever  portion  of  the  foundation  exceeds 
sixty  pounds  per  square  inch,  reinforcement  is  necessary. 


The  foundation  is  generally  considered  as  being  similar  to  a  column  looting. 
I  lie  outstanding  cantilever  portion  of  the  base  is  acted  upon  by  the  upward  earth 
pressure  so  that  tension  exists  on  the  lower  side,  while  the  remainder  may  be  con¬ 
sidered  as  a  fixed  plate  with  tension  on  the  upper  side.  It  is  customary  to  de¬ 
termine  the  bending  moment  per  unit  of  width  and  calculate  the  amount  of  steel 
required  in  accordance  with  the  formula  given  below.  In  making  these  calcula¬ 
tions,  account  should  be  taken  of  the  fact  that  the  soil  pressure  does  not  vary 
uniformly. 

M  =jdAss 

where  d  =  distance  from  the  compressive  face  to  the  plane  of  the  steel; 

M  =  resisting  moment  as  determined  by  steel; 
j  =  constant  which  may  be  taken  as  0.875; 

As  =  area  of  cross-section  of  steel; 

(Note.  —  For  octagons  use  55%  of  computed  value) 
s=unit  fiber  stress  in  steel. 

I  he  shearing  stresses  should  also  be  examined  to  see  that  they  are  within  safe 
limits.  The  punching  shearing  stress  is  equal  to  the  total  upward  soil  pressure  on 
the  area  under  consideration,  divided  by  the  shearing  area  of  the  foundation. 

Foundations  supported  on  piles  are  treated  in  accordance  with  the  general 
cantilever  formula,  except  that  the  second  moment  for  a  system  of  piles  is  found  in 
accordance  with  the  principle  stated  on  page  65. 

Foundations  supported  on  piles  having  large  bearing  power  should  have  the 
reinforcing  designed  to  take  care  of  both  the  circumferential  and  radial  bending 
moments. 

Before  proceeding  with  design  and  static  calculations  it  is  necessary  to  assign 
certain  values,  such  as  the  values  of  wind  pressure,  stresses  allowable  in  the  brick¬ 
work,  as  well  as  the  weight  of  the  brickwork  in  place.  Also  consideration  must  be 
given  to  the  thermal  stresses  set  up  in  the  walls. 

These  are  rather  involved  subjects  upon  which  there  has  been,  and  still  is,  a 
great  diversity  of  opinion.  They  will,  t  herefore,  be  treated  under  separate  headings, 
setting  forth  the  combined  results  of  the  best  known  modern  investigators,  as  well 
as  the  experience  of  the  Custodis  Company  covering  a  period  of  over  forty  years. 

WIND  PRESSURE 

Winds  are  due  to  the  differences  in  the  atmospheric  density  produced  l>\  the 
sun  in  its  unequal  heating  of  the  earth  and  its  surrounding  atmosphere.  These 
differences  constitute  a  condition  of  unstable  equilibrium.  The  air  immediately 
moves  to  restore  equilibrium  and  as  a  result  sets  up  vertical  and  horizontal  wind 
currents. 

Ihe  differences  in  density  which  are  produced  depend  upon  the  geographical 
location  and  climatic  conditions.  Flic  wind  velocities  attained,  therefore,  vary 
widely  in  the  different  parts  of  the  world. 


The  United  States  W  eather  Bureau  for  a  long  period  has  kept  a  daily  record  of 
wind  velocities.  The  map  on  page  71  shows  the  maximum  recorded  velocities  in 
the  various  parts  of  the  United  States.  A  study  of  this  map  shows  that  recognition 
should  be  given  to  regional  differences  in  maximum  wind  velocity  in  chimney 
design. 

The  maximum  velocities  indicated  are  the  recorded  velocities  from  the  Robin¬ 
son  Anemometer.  They  are  not  the  actual  velocities.  Mr.  P.  C.  Day,  Meteorologist 
Weather  Bureau,  Department  of  Agriculture,  writes  under  date  of  Oct.  29,  1923: 

“The  relation  between  indicated  velocity  as  published  and  actual  velocity  of 
the  wind  has  been  recently  made  the  subject  of  experiments  in  the  wind  tunnel  of 
the  Bureau  of  Standards.  The  results  may  be  taken  from  the  following  tables: 

Miles  per  I  lour 


Indicated  velocity .  10.0  20.0  30.0  40.0  50.0  60.0 

Actual  velocity .  9.1  17.1  21.9  32.2  39.5  17.0 

Indicated  velocity .  70.0  80.0  90.0  100.0  110.0  120.0 

Actual  velocity .  54.3  61.7  69.0  76.3  83.6  91.1 

Indicated  velocity .  130.0  140.0  150.0 

Actual  velocity .  98.5  106.0  113.3” 

_ 


In  predicting  the  probable  maximum  wind  velocity  which  the  chimney  will 
have  lo  withstand,  consideration  should  be  given  to  the  fact  that  the  recording 
instruments  are  recording  rather  than  integrating,  so  that  it  is  possible  that  the 
velocities  of  occasional  gusts  are  60%  higher  than  those  recorded. 

The  development  of  aviation  necessitated  an  exhaustive  and  comprehensive 
study  of  wind  velocities  and  pressures.  It  is  a  fact  that  the  velocities  increase  with 
the  height  above  ground.  This  must  be  considered  in  the  design  of  all  chimneys, 
more  especially  the  very  tall  ones. 

Some  very  accurate  data  has  been  secured  through  careful  experiments  at 
AIcCook  Field,  Dayton,  Ohio,  of  which  Mr.  E.  A.  Fales,  Aeronautical  Engineer, 
writes  under  date  of  Nov.  16.  1923: 

“A  reasonable  velocity  gradient  curve  can  be  given  only  for  the  case  of  Hat 
unobstructed  ground.  To  consider  this  curve  a  straight  line  seems  consistent  for 
practical  use  in  chimney  design. 

“McCook  Field  experiments  with  pilot  balloons  (1921-22)  indicated  that  the 
velocity  at  altitudes  up  to  5,000  ft.  was  represented  by  the  equations 

V  =  /  2400  1 )  ^  1  ^0r  avera&e  winds 

V  =  ( — r — hi )  Vi  for  highest  winds  observed 

V  8550  /  8 

Where  Y  =  velocity  at  an  altitude 

Vi  =  velocity  near  the  ground 
h  =  height  in  feet." 


70 


71 


The  velocity  of  the  wind  near  the  ground  depends  largely  upon  the  nature  of 
the  surrounding  terrain. 

The  determination  of  what  pressure  a  wind  of  given  velocity  produces  on  a 
given  surface  has  been  a  subject  of  controversy  for  many  years  and  there  are  many 
different  values  published  in  the  various  hand  books  on  engineering.  The  reason 
for  this  lack  of  agreement  is  well  explained  by  Mr.  Tales,  who  says,  “The  wind 
force  on  chimneys  cannot  be  determined  in  any  other  manner  than  by  actual 
empirical  measurement.  It  cannot  be  computed  from  known  laws  of  physics; 
for  the  behavior  of  air  flowing  past  any  sort  of  object  is  not  well  understood. ” 

The  method  in  the  past  has  been  to  determine  values  for  flat  surfaces,  then 
apply  a  correction  factor  for  the  various  forms  of  profile.  Among  the  values  most 
frequently  found  are 

P  —  .0032 \  ■  on  flat  surfaces  (Stanton) 

P  =  .0040v2  on  flat  surfaces  (U.  S.  Weather  Bureau) 

P  =  .0023v2  on  flat  surfaces  (Welsbach) 

P  =  .0021  lv2  on  flat  surfaces  (Mariotte) 

P  =  .00535v2  on  Hat  surfaces  (French  Government) 

Regarding  this  Mr.  P.  C.  Day  of  the  Weather  Bureau  says: 

“  A  careful  study  of  wind  pressures,  w  ith  special  reference  to  their  application 
to  aviation,  was  made  by  Mr.  E.  Eiffel.  Paris,  and  a  translation  by  Hunsaker, 
assistant  naval  constructor,  U.  S.  Navy,  published  1913,  will  no  doubt  be  available 
in  a  local  library.  The  general  formula  for  small  plates  exposed  normal  to  the 
wind  is: 

P  =0.0033SV2 

in  which  P  equals  the  pressure  in  pounds,  S  equals  the  area  of  the  surface  in  square 
feet,  and  \  equals  the  true  velocity  of  the  w  ind  in  miles  per  hour.  This  result  is 
somewhat  lower  in  value  than  that  determined  by  some  experiments  made  by  the 
W  eat  her  Bureau  some  years  ago  in  which  the  factor  0.004  was  adopted,  it  seems 
quite  likely  that  with  the  better  appliances  used  by  Mr.  Eiffel,  his  value  is  the 
better  one.” 

For  round  surfaces,  American  engineers  use  values  for  the  projected  area 
ranging  from  one-half  to  two-thirds,  while  continental  engineers  use  two-thirds. 

Mr.  Fales  has  investigated  this  matter  and  writes  under  date  of  Nov.  16,  1923: 

“  As  affects  cylinder  resistance,  sufficient  work  has  been  done  to  show  that  a 
maximum  value  of  the  resistance  coefficient  may  be  reasonably  used  where  the 
cylinder  is  of  large  diameter  as  in  the  case  of  a  chimney. 

“Theory  and  experiment  indicate  that  the  resistance  coefficient  within  certain 

.  i  ,  « „  ,  ,  ,T  ,  .  /  Velocity  X  Diam.  \ 

ranges  depends  upon  the  Kevnolds  Number  17: - : - — — -  • 

&  1  1  ‘  \ Viscosity  Coefficient/ 

“If  the  coefficient  be  plotted  against  this  ‘  Reynolds  Number’  the  curve,  as  the 
velocity  or  diameter  increases,  first  drops  25%,  then  rises  back  to  its  original  value 
and  then  drops  off.  approaching  a  minimum  value  when  velocity  X  diameter 
reaches  70.0  (velocity  in  ft.  per  sec.,  diameter  in  ft.,  viscosity  coefficient  remaining 


the  same  throughout).  Now  in  the  case  of  large  cylinders  whose  length  is  great 
enough  to  make  the  end  effect  negligible,  the  Reynolds  Number  is  5  to  50  times 
greater  than  this.  The  indications  are  that  no  further  rise  takes  place  in  the 
coefficient  as  VxD  is  increased  beyond  70.0.  Therefore,  the  best  information 
available  from  different  sources  indicates  that  this  coefficient  represents  I  he  maxi¬ 
mum  resistance  to  be  expected  in  large  diameters  and  high  wind  velocities. 

“  There  results  the  following  formula  which  may  be  applied  to  circular  chimneys, 
with  the  satisfaction  of  knowing  that  there  is  no  better  coefficient  obtainable  from 
any  source  whatsoever: 

It  =  .0022  DV2 

where  (It)  is  the  resistance  per  linear  foot  of  chimney. 

(D)  is  chimney  diameter  in  feet 
(V)  is  wind  velocity  in  miles  per  hour. 

This  coefficient  has  been  arrived  at  from  study  of  various  tests,  and  in  particular 
those  of  Dry  den  (see  paper  394,  U.  S.  Bureau  of  Standards).” 

It  is  interesting  to  note  that  using  a  profile  correction  factor  of  2/3  Mr.  Bales 
checks  Mr.  Eiffel  exactly. 

For  octagon  surfaces  American  engineers  use  values  for  the  projected  area  of 
0.75,  while  continental  engineers  use  0.71. 

COMPRESSIVE  STRENGTH  OF  BRICKWORK 

The  compressive  strength  of  brick  masonry  depends  upon  the  quality  of  the 
brick,  mortar  and  workmanship. 

A  study  of  the  behavior  of  various  specimens  of  brick  masonry  under  com¬ 
pression  in  a  testing  machine  shows  that  tendency  is  for  the  individual  brick  to 
fail  by  flexure  due  to  the  non-uniform  distribution  of  the  test  load.  This  non- 
uniform  distribution  is  due  to  the  irregularity  in  the  shape  of  the  bricks,  the  human 
equation  in  the  jointing  of  the  specimen  pier,  and  the  displacement  of  the  mortar 
under  load. 

Many  formulas  are  available  in  the  engineering  handbooks  for  calculating 
the  strength  of  common  brick  piers.  The  formulas  given  by  the  U.  S.  Bureau  of 
Standards  are 

P  =  Ivp  (1) 

P  =  KR  (2) 

Where  P  =  unit  ultimate  compressive  strength  of  pier 

Where  p=unit  ultimate  compressive  strength  of  single  bricks 

Where  R  =  unit  transverse  strength  of  modulus  of  rupture  of  the  single  bricks 
K  =  constant  depending  upon  the  kind  of  mortar  used. 

The  following  formula  for  the  strength  of  perforated  radial  brick  masonry  was 
derived  from  the  results  secured  at  the  Royal  Mechanical  Technical  Institute  of 
Tests  at  Chariot  tenburg. 


K  = . 


26Ivs  1  + 


8  Km  \ 
Ks  ' 


Where  K  =  compressive  strength  of  masonry  in  kg.  per  sq.  cm. 

Km  =  compressive  strength  of  mortar  in  kg.  per  sq.  cm. 

Ks  =  compressive  strength  of  brick  in  kg.  per  sq.  cm. 

It  is,  therefore,  evident  that  compressive  strength  of  the  brickwork  depends 
to  a  large  extent  upon  the  strength  of  the  brick  used.  Care,  therefore,  should  be 
taken  to  see  that  the  brick  are  of  good  quality.  To  that  end  the  C.ustodis  Company 
frequently  test  their  brick  and  know  the  crushing  strength  of  all  their  materials. 

Different  experimenters  often  obtain  widely  varying  results  in  testing  the 
same  quality  brick.  This  is  because  the  values  obtained  depend  upon  the  dimen¬ 
sions  of  the  specimen  tested,  the  method  of  preparation  and  the  method  of  applying 
the  test  load.  The  samples  should  have  their  faces  ground  so  that  they  are  abso¬ 
lutely  parallel  or  else  imbedded  in  plaster  j  tar  is  or  portland  cement  and  the  load 
applied  gradually.  Good  judgment  is,  therefore,  needed  to  interpret  the  results 
obtained  in  the  tests  of  the  individual  bricks. 

In  compression  the  mortar  is  invariably  weaker  than  the  brick.  Consequently 
under  excessive  loads  it  yields  and  is  displaced.  Therefore,  the  mortar  to  a  con¬ 
siderable  extent  determines  the  strength  of  the  brickwork. 

Theoretically  the  thinner  the  joints  the  nearer  the  strength  of  the  brickwork 
approaches  the  strength  of  the  single  bricks.  In  practice  the  joints  must  be  thick 
enough  to  properly  bed  the  brick  to  an  even  bearing. 

If  the  joints  are  very  thin  the  brick  are  liable  to  absorb  enough  water  from 
the  mortar  to  prevent  its  proper  hardening. 

Brick  with  low  absorption  power  are  not  always  desirable  in  chimney  work. 
They  are  difficult  to  hold  in  position  on  the  wall  and,  furthermore,  they  do  not 
absorb  enough  water  to  give  the  maximum  adhesion  between  mortar  and  brick. 
Soft  bricks,  on  the  other  hand,  rol)  the  mortar  of  water,  defeating  the  hardening 
process. 

It  is  specified  at  times  that  the  compressive  stress  on  the  brickwork  shall  not 
exceed  one-tenth  the  ultimate  strength  of  the  single  bricks. 

In  chimney  work  to  limit  the  compression  to  350  pounds  per  square  inch  is 
good  judgment. 


WEIGHT  OF  MASONRY 

All  self-supporting  brick  chimneys  are  dependent  upon  the  force  of  gravity 
to  prevent  overturning  by  wind  pressure.  Therefore,  the  unit  weights  of 
the  masonry  which  are  used  in  determining  the  stresses  should  be  the  accurate 
results  of  experience  and  experiment,  otherwise  the  results  of  stability  calculations 
will  be  of  little  value.  It  is  obvious  that  the  weight  of  the  brickwork  depends 
entirely  upon  the  weight  of  the  various  materials  of  which  it  is  composed,  namely, 
the  weight  of  the  bricks,  the  sand,  the  cement  and  the  lime.  The  weight  of  the 


74 


mortar  varies  somewhat,  hut  not  between  as  wide  limits  as  the  brick  itself.  The 
weight  of  brick  is  dependent  upon  the  nature  of  the  clay,  the  porosity  of  the 
finished  product,  the  method  of  manufacture  and  the  hardness  of  burn. 

The  weight  of  sand  varies,  depending  upon  its  composition,  its  coarseness 
and  geological  origin.  The  weight  of  cement  and  good,  pure,  wood-burned  lime 
is  comparatively  constant,  the  cement  especially  being  manufactured  under 
laboratory  supervision.  The  products  of  different  brickyards  vary  in  texture, 
density  and  weight.  It  is,  therefore,  a  fallacy  to  compare  the  weight  and  stability 
of  a  radial  brick  chimney,  built  of  radial  bricks,  light  in  weight,  approaching  the 
structure  and  hollow  form  of  partition  fireproofing  with  a  radial  brick  chimney 
built  of  dense,  hard  burned,  impervious,  heavy,  properly  designed  radial  brick. 
The  design  of  the  radial  brick  itself  as  well  as  its  physical  characteristics  should 
be  given  careful  consideration  of  all  who  propose  building  a  radial  brick  chimney. 

TEMPERATURE  STRESSES 

The  walls  of  a  brick  chimney  are  heated  on  the  inside  by  the  hot  flue  gases, 
while  the  outside  portion  of  the  walls  remain  practically  at  atmospheric 
temperatures.  The  drop  in  temperature  through  the  wall  is  practically  uniform. 
This  results  in  the  inner  portion  of  the  wall  expanding  circumferentially  and 
vertically,  while  the  outer  portion  endeavors  to  remain  in  its  original  position, 
setting  up  tension  in  the  outer  ring  and  compression  in  the  inner  ring.  The 
magnitude  of  the  stresses  depends  upon  the  temperature  of  the  smoke  stream  and 
upon  the  modulus  of  elasticity  of  the  mortar  and  the  brick.  If  the  circumferential 
temperature  stresses  on  the  outside  exceed  the  ultimate  strength  of  the  masonry 
in  the  outer  ring  a  rupture  will  occur.  Lime  mortar  is  more  compressible  and 
more  elastic  than  a  sand  cement  mortar.  It  is  for  that  reason,  in  construction  of 
chimneys,  a  goodly  quantity  of  lime  is  used  with  the  cement  in  the  mortar. 
This  increases  the  elastic  limit  of  the  joint  and  thereby  greatly  reduces  the  ten¬ 
sile  stresses  in  the  outer  ring.  To  further  assist  in  taking  up  the  hoop  stresses, 
steel  bands  are  built  at  intervals  in  the  outer  portion  of  the  chimney  wall. 

For  this  same  reason  adequate  amount  of  lining  is  advocated  to  insulate  the 
main  walls  of  the  chimney,  thus  protecting  the  inside  portion  from  excessive  tem¬ 
peratures.  This  is  the  governing  factor  in  the  design  of  high  temperature  chimneys, 
the  object  being  to  reduce  the  temperature  gradient  between  the  inner  and  outer 
portions  of  the  main  walls. 

The  tendency  of  the  inner  portion  of  the  walls  to  expand  vertically  is  taken  up 
by  the  elasticity  of  the  lime  cement  mortar  and  the  strong  bond  of  the  perforated 
radial  brickwork.  Ruptures  in  the  main  walls  of  the  chimneys  due  to  vertical 
expansions  are  practically  unknown;  the  circumferential  stresses,  however,  should 
be  given  careful  consideration. 

In  general  this  is  a  complicated  subject  on  which  little  exact  information  is 


available,  but  the  Custodis  Company’s  many  years  of  experience  enable  them  to 
readily  cope  with  these  temperature  stresses. 

It  is  therefore  essential  that  the  maximum  temperature  expected  be  known 
and  the  chimney  be  designed  accordingly. 


SAMPLE  OF  CALCULATIONS 


Factory  chimney  150'  0"  high  by  8'  6"  inside  diameter  at  top  serving  a  boiler 
plant  at  Binghamton,  New  York.  The  chimney  and  various  types  of  foundation 
are  shown  in  figures  88.  39,  40  and  41,  page  77.  It  is  built  of  radial  brick  on  foun¬ 


dation  of  concrete. 

1  cubic  foot  of  radial  brick  masonry  weighs . 120  pounds 

1  cubic  foot  of  concrete  weighs . 150  pounds 


The  method  of  calculations  and  the  symbols  used  are  the  ones  shown  in  the  pre¬ 
ceding  pages. 

The  wind  pressure  is  taken  as  22 1  2  pounds  per  square  foot  of  projected  area. 
The  foundations  are  designed  so  that  there  is  no  tendency  to  lift,  on  the  wind¬ 
ward  side. 


Cl IIMMA  CALCUL \T1( >N S 


( 1)  olume 


Section 

Length 

1 

20' 

9 

20' 

3 

20' 

1 

20' 

5 

20' 

6 

20' 

( 

20' 

8 

10' 

2)  Weight 

p  5874x120 
2000 

353  tons 

(Slide  Rule  t  sed) 

\\  all  Thickness  \  olume  of  Section 


~Vs 

351  cubic  feet 

m 

1 18  cubic  feet 

10  Xs 

576  cubic  feet 

13 

736  cubic  feet 

15 

886  cubic  feet 

17 

10 12  cubic  feet 

18Vs 

1170  cubic  feet 

20  y8 

665  cubic  feet 

5874  cubic  feet 

(3)  \\  ind  Pressure 


W 


9.69  +  1 1. 19)  X  150x22.5 


2x2000 

(4)  Lever  arm  of  resultant  wind  pressure 
[14.49  +  (2  X 9.69)]  X 150 


=  20. 12  tons 


L 


(9.69  +  14.49)  X3 


=  70.0  feet 


O  -07 


y-fpw? 


(5)  W  ind  moment  at  foot  of  chimney 

M  =20.42  xTO.O  =  1430  feet  tons 

(6)  Radius  of  resultant 

»  1430  f  . 

A  -  =1.0 o  leet 

353 

(7)  Radius  of  first  kern 

(For  hollow  circular  section  R  =  .250  1  +  f  J  R 

R  =  .250  £  1  +  J  7.245  =2.88  feet 

(8)  Radius  of  second  kern 

1- 


For  hollow  circular  section  e  = 


3tt 

16 


r 

R 

r 

R 


R 


e  = 


16 


5.565 

7.21.5 


5.565 x 
55245 


7.2 15  =  5.09  feet 


(9)  Net  area  at  foot 

A=7r  (7.2452  —  5.5652)  =67.5  square  feet 

(10)  Stress  intensity  at  foot  lee  side 

S"  =  1  +  =  12.60  tons  per  square  foot 

67.5  \  2.88/ 

(11)  Stress  intensity  at  foot  windward  side 


s„ =  3o3  ,  ^ 


4.05  \ 


=  — 2.12  tons  per  square  foot 


67.5\'  2.88/ 

(12)  Maximum  stress  intensity  at  foot  lee  side 

S'"  =  1: 


[2.60  — r — 2.12  (  I  =13.2  tons  per  square  foot 

J_  \  5.09 — 2.88/  _J 


FOUNDATION  CALCULATIONS 

Solid  type — no  steel  reinforcing — For  dimensions  See  Fig.  39,  page  77 
Maximum  allowable  soil  pressure  =2}/£  tons  per  square  foot 


78 


(13)  Weight  of  foundation  =  151  tons 

(1  f)  W  eight  of  chimney,  lining,  foundation  and  lill  =556  tons 

(15)  Wind  moment  at  foot  of  foundation  =  1552  foot  tons 

(16)  Area  of  foundation  =438.2  square  feet 

(17)  Section  modulus  of  foundation  =  1332.3  feet3 

(18)  Soil  pressure  =  3  _  +  =2.43  tons  per  square  foot 

438.2  1332.3 

(19)  Tension  in  concrete 

M  6550  _  ,  ,  .  , 

p  =  =  =57.1  pounds  per  square  inch 

V  1 1  o2 


Reinforced  concrete  type.  For  dimensions,  see  Fig.  40,  page  77 


(20)  Weight  of  foundation  =  128  tons 

(21)  Weight  of  chimney,  lining,  foundation  and  lill  =509  tons 

(22)  Wind  moment  at  foot  of  foundation  =1522  foot  tons 

(23)  Area  of  foundation  =419.3  square  feet 

(24)  Section  modulus  of  foundation  =1247.3  feet:! 


(25)  Soil  pressure 

(26)  Tension  on  concrete 


509  1522 

+ 


1247.3 


=  2.43  tons  per  square  foot 


p  =  y  =  =  8d.O  pounds  per  square  inch 

(27)  Reinforcing  steel  required 
4.00x4860x24 


As  = 


V8X  4X12X16000 


X  .55  =  .38  square  inch 


PILE  FOUNDATIONS 

Same  foundation  with  concrete  piles  capable  of  sustaining  a  load  of  25  tons 
per  pile.  (See  Fig.  41,  page  77) 

(28)  Dead  load  on  piles  =  509  tons 

(29)  Number  of  piles  =  38 

(30)  Dead  load  per  pile  — ^r—  =13.35  tons 

38 

(31)  Wind  moment  at  foot  of  foundation  =  1522  foot  tons 


79 


Moment  of  inertia  of  system  of  piles  about  the  horizontal  axis  =  1398 
e.  g.  pile  #1  1  +  (1  X 102)  =  101 

(33)  Section  modulus  of  system  of  piles  about  the  horizontal  axis  =  139.8 

1522 


Live  load  per  pile  =  -  =  10.85  tons 

1  1  139.8 

(35)  Total  load  per  pile  =  13.35  +  10.85  =24.20 

For  the  convenience  of  the  designer,  we  give  the  following  tables  showing  the 
dimensions  of  Custodis  radial  brick  chimneys  and  foundations: 

TABLE  9 

CHIMNEY  DIMENSIONS  AND  WEIGHTS 
Following  dimensions  and  weights  are  approximate  and  must  not  be  used  as  final 
Boiler  Chys.  Normal  Conditions.  Temperatures  not  above  800  degree  Fahrenheit 


A 

B 

c 

D 

E 

Lining 

Total  Wt. 
Erect. 
(Dead) 

Approx. 

H.  P.  1  lb.  C. 

A 

B 

c 

D 

E 

Lining 

Total  Wt. 
Erect 
(Dead) 

Approx. 

H.  P.  4  lb.  C. 

80' 

3' 

8'-  1 V 

15  V 

7V 

15' 

69  Tons 

205 

225' 

7' 

17'-  6 V 

28" 

7V 

40' 

655  Tons 

1875 

80' 

4' 

8'-  9" 

I5V' 

7  \A" 

15' 

78  “ 

364 

225' 

8' 

17'-10V 

28" 

7  V 

40' 

688  “ 

2451 

100' 

4' 

9'-10  V 

19" 

7  V 

15' 

hi  “ 

410 

225' 

9' 

18'-  3V 

28" 

7  V 

40' 

716  “ 

3101 

100' 

5' 

10'-  8" 

17" 

7!+" 

15' 

124  “ 

637 

225' 

10' 

18'-  9 A" 

28" 

714" 

40' 

7  57 

3829 

100' 

6' 

10'-I  1 V 

17" 

734* 

15' 

132  “ 

920 

225' 

12' 

19'-  7  V 

27" 

8V 

40' 

830  “ 

5515 

L 10' 

4' 

10-11 

19" 

7 

20' 

113  “ 

429 

250' 

8' 

19'-  1%" 

29" 

714" 

45' 

844  “ 

2584 

1 10' 

5' 

11'-  2" 

10" 

7V 

20' 

148  “ 

669 

250' 

9' 

19'-  6  V 

29" 

714" 

45' 

880  “ 

3269 

110' 

6' 

11'-  5M" 

19" 

7  V 

20' 

157  “ 

962 

250' 

10' 

20'-  <>V 

29" 

7 14" 

45' 

925  " 

4037 

125' 

5' 

11-11" 

21" 

7  34" 

20' 

185  “ 

715 

250' 

12' 

20'-10V 

28" 

nyH" 

45' 

1003  “ 

581 1 

125' 

6' 

12'-  2  V 

21" 

7  V 

20' 

193  “ 

1051 

250' 

14' 

22'-  IV 

97  " 

a  A" 

45' 

1068  “ 

7940 

135' 

5' 

12'-  4 34" 

21" 

7V 

20' 

213  “ 

744 

275' 

9' 

20'-  9 A" 

30" 

7  14  " 

50' 

1065  “ 

3440 

135' 

6' 

12'-  8V 

21" 

734" 

20' 

221  “ 

]  092 

275' 

10' 

21  3  V 

30" 

7  J4" 

50' 

m2  “ 

4243 

150' 

5' 

13'-  2" 

23V 

734" 

25' 

263  “ 

797 

275' 

12' 

22'-  IV 

29' 

8%" 

50' 

1192  “ 

6090 

150' 

6' 

13'-  5  V 

23  A" 

7  34  " 

25' 

273  “ 

1  147 

975' 

14' 

23'-  4  V 

28" 

;;  . 

50' 

1262  “ 

8300 

150' 

7' 

13'-  9  V 

23  V 

7V 

25' 

292  “ 

1 563 

300' 

14' 

24'-  7 A" 

30" 

8  %  " 

50' 

1480  “ 

8670 

150' 

8' 

14'-  >%" 

23  V 

7V 

25' 

3 1  1  “ 

2041 

300' 

15' 

25'-  2  A" 

30" 

8  - 

50' 

1550  “ 

9940 

160' 

(V 

is'- mr 

23  V  " 

7  V 

25' 

310  “ 

1185 

300' 

16  '-6" 

25'-  8 

32" 

10  V 

50' 

1688  “ 

1221(1 

160' 

7' 

14'-  3 V 

23  V 

7  V 

25' 

330  “ 

1615 

300' 

18' 

27'-  8" 

40" 

L0V 

50' 

2113  “ 

1 4360 

160' 

8' 

14'-  73s" 

23  V 

25' 

349  “ 

2102 

300' 

20' 

30'-  4" 

38" 

ny4 " 

50' 

2235  “ 

17700 

175' 

7' 

15'-  0  V 

25" 

714' 

30' 

395  “ 

1654 

325' 

14' 

25'-10V 

34' 

8 

55' 

1746  “ 

9025 

175' 

8' 

15'-  4%" 

25" 

734" 

30' 

416  ' 

2161 

325' 

15' 

26'-  6 A" 

34" 

HA" 

55' 

1820  “ 

10370 

175' 

9' 

15'-  9 A" 

25" 

714" 

30' 

441  “ 

2734 

325' 

IO'-6" 

27'-  2%‘ 

34" 

10  yH" 

55' 

1960  “ 

12750 

175' 

10' 

16'-  h3V 

26  A" 

714' 

30' 

494  “ 

3374 

325' 

18' 

31-  2" 

32" 

10%' 

55' 

2020  “ 

14920 

200' 

7' 

16'-  3 v 

26  A" 

7  V 

35' 

516  “ 

1768 

325' 

20' 

31-  4" 

40" 

11 V 

55' 

2620  “ 

18440 

200' 

8' 

16'-  73  s" 

26  A" 

7V 

35' 

540  “ 

231  1 

350' 

15' 

27'-  9  V 

36" 

av 

60' 

2120  “ 

10750 

200' 

9' 

17'-  0 A" 

26  V 

714" 

35' 

570  “ 

2925 

350' 

16  '-6" 

28'-  23  k" 

36" 

10  V 

60' 

2280  “ 

13200 

200' 

10' 

17'-  6k>" 

26  V 

35' 

605  “ 

36 1  1 

350' 

18' 

33'-  iy2" 

36" 

10V 

60' 

2520  “ 

15500 

200' 

12' 

18'-  -IV8" 

25" 

8H' 

35' 

675  “ 

5200 

350' 

20' 

32'-  4" 

44" 

11%' 

60' 

3075  “ 

1 9 1 50 

TABLE  10 

FOUNDATION  DIMENSIONS 


AND  VOLUMES 


Two  Ton 

Two  and  One-Half  Ton 

Three  Ton 

Depth 

No. 

Weight 

Size 

Type 

in 

of 

of 

l  op  Dia. 

Bottom 

Cu.  Yds. 

Cu.  Yds. 

1  op  Dia. 

Bottom 

Cu.  Yds. 

Cu.  Yds. 

1  op  Dia. 

Bol  tom 

Cu.  Yds. 

Cu.  Yds. 

Feet 

Slabs 

Chimney 

Dia. 

Cone. 

Excav. 

Dia. 

Cone. 

Excav. 

Ilia. 

Cone. 

Excav. 

80'x  4' 

4 

9 

9'  0" 

12'  0" 

16.7 

21.4 

9'  0" 

11'  0" 

15.0 

17.9 

80'x  4' 

4 

9 

10'  6" 

13'  6" 

17.9 

99  4. 

90'x  5' 

Sq. 

4 

9 

10'  6" 

13'  0" 

20.7 

25.0 

10'  6" 

12'  6" 

19.8 

23.2 

90'x  5' 

Oct. 

4 

2 

11' 9" 

15'  0" 

22.3 

27.6 

1 00'x  4' 

4 

2 

10'  6" 

14'  0" 

22.6 

29.1 

10'  6" 

13'  0" 

20.7 

25 . 0 

100'x  4' 

Oct. 

4 

2 

12'  0" 

15'  6" 

23 . 6 

29.5 

100'x  6' 

Sq. 

4 

2 

132  tons 

11'  9" 

15'  0" 

26.9 

33 . 3 

11'  0" 

14'  0" 

23  5 

29.0 

11'  0' 

13'  0" 

21.5 

25.0 

100'x  6' 

Oct. 

4 

9 

13'  9" 

17'  0" 

29.4 

125'x  5' 

Sq. 

5 

3 

185  tons 

12'  6" 

17'  6" 

42.4 

56 . 6 

12'  6" 

16'  0" 

38 . 0 

47  4 

12'  6" 

15'  0" 

35 . 2 

41  7 

125'x  5' 

Oct. 

5 

3 

185  tons 

13'  0" 

19'  6" 

11  2 

58 . 3 

13'  6" 

18'  0" 

38 . 4 

49.7 

12'  6" 

17'  0" 

33  8 

44 . 3 

125'x  7' 

Sq. 

5 

3 

225  tons 

13'  6" 

18'  6" 

48.2 

63 . 5 

13'  6" 

17'  0" 

43 . 4 

52 . 5 

13'  6" 

16'  0" 

40 . 5 

17  1 

125'x  7' 

Oct. 

5 

3 

225  tons 

15'  6" 

20'  6" 

50 . 2 

64.6 

15'  0" 

19'  6" 

55  3 

58  3 

14' 0" 

18'  6" 

ID  8 

52 . 5 

150'x  4' 

Sq. 

6 

3 

255  tons 

14'  0" 

20'  0" 

65 . 5 

89.0 

14'  0" 

18'  0" 

57.5 

72.0 

14'  0" 

17'  0" 

53 . 8 

64  1 

150'x  4' 

Oet. 

6 

3 

255  tons 

15'  6" 

22'  0" 

66 . 6 

89.1 

15'  0" 

20'  6" 

59 . 5 

77.5 

14'  0" 

19'  0" 

51 .0 

66  5 

150'x  6' 

Sq. 

6 

3 

273  tons 

15'  0" 

21'  0" 

73.4 

98.0 

15'  0" 

19'  0" 

64  9 

77.0 

15'  0" 

18'  0" 

61.0 

19  9 

150'x  6' 

Oct. 

6 

3 

273  tons 

17'  0" 

23'  6" 

76.8 

101 . 5 

16'  0" 

21'  6" 

65 . 6 

85.2 

15' 6" 

20'  6" 

64  0 

77  5 

150'x  8' 

Sq. 

6 

3 

311  tons 

16'  0" 

22'  0" 

81.6 

107.6 

16'  0" 

20'  0" 

72.6 

88  9 

16'  0" 

19'  0" 

68  4 

80 . 3 

150'x  8' 

Oct. 

6 

3 

311  tons 

18'  0" 

24'  6" 

84.5 

110.8 

17'  6" 

23'  0" 

76.3 

97.7 

16'  0" 

21'  6" 

65.7 

83  5 

175'x  7' 

Sq. 

7 

3 

395  tons 

16'  0" 

24'  0" 

106  1 

149.9 

16'  0" 

22'  0" 

95  1 

123.5 

16'  0" 

20'  0" 

84.8 

1 03 . 7 

175'x  7' 

Oct. 

7 

3 

395  tons 

19'  0" 

26'  6" 

113.0 

150.6 

18'  0" 

24'  6" 

98  3 

128.9 

17'  0" 

23'  0" 

87.0 

1  1  1  11 

175'x  9' 

Sq. 

7 

3 

441  tons 

17'  6" 

25'  6" 

122.0 

169.2 

17'  0" 

23'  0” 

105.0 

137 . 2 

16'  6" 

21'  0" 

91.8 

114.2 

175'x  9' 

7 

3 

441  tons 

200'x  7' 

Sq. 

8 

4 

516  tons 

18'  0" 

27'  6" 

158  0 

224 . 5 

16'  6" 

25'  0” 

130.8 

183.3 

16'  6" 

23'  0" 

117.2 

157.0 

200'x  7' 

<  >ct. 

8 

1 

200'x  9' 

Sq. 

8 

4 

570  tons 

19'  0" 

29'  0" 

177 . 0 

249 . 7 

17'  6" 

26'  0" 

143.0 

199.8 

17'  6" 

24'  0' 

129.6 

170.5 

80 


Chapter  V 
FOUNDATIONS 

Just  as  the  determination  of  the  proper  height  and  diameter  of  a  chimney  for 
a  particular  case  is  invariably  a  problem  of  its  own,  so  the  foundation  design  is  one 
to  properly  meet  the  soil  conditions  encountered  as  well  as  the  general  conditions 
in  reference  to  building  walls  and  structures  in  the  immediate  vicinity. 

A  chimney  is  a  structure  subjected  to  shock  due  to  the  sudden  increases  and 
decreases  in  the  velocity  of  the  wind. 

These  abrupt  changes  of  wind  pressure  produce  the  dynamic  effect  of  a  sud¬ 
denly  applied  load.  The  soil  then  must  have  sufficient  bearing  power  to  resist  this 
in  addition  to  the  dead  load  and  pressure  produced  by  the  wind  force.  For  this 
reason  in  the  case  of  chimneys  we  counsel  more  conservative  loadings  than  are 
allowed  in  ordinary  foundations,  especially  if  the  soils  are  low  in  bearing  power. 
All  soils  are  compressible  to  some  extent.  The  design,  therefore,  should  aim  to 
reduce  settlement  to  a  minimum  and  provide  so  that  if  there  is  any  settlement,  it 
will  be  uniform. 

Silty  soils,  mud  and  quicksand  have  low  bearing  power  and  are  liable  to  squeeze 
out  in  everyr  direction  when  a  heavy  load  is  applied,  and  should  never  be  relied 
on  for  a  foundation. 

Clay  soils  vary  widely  in  their  bearing  power,  as  they  range  from  shale  down 
to  soft  clay  which  oozes  under  slight  pressure.  The  bearing  power  of  clay  soils 
is  lowered  by  the  penetration  of  water  and  it  is  desirable  to  provide  drainage  for 
the  foundation.  Where  soft  clay  is  encountered  care  should  be  taken  to  see  that 
there  is  no  possibility  of  the  soil  escaping  by  flowing  into  ad  jacent  foundations. 

Hard,  stiff,  dry  clay  in. thick  beds  generally  has  a  bearing  capacity  of  2§  tons 
per  square  foot.  11  ‘ 

Soft,  wet  clay  dannot  be  relied  on  to  carry  more  than  1  ton  per  square  foot. 
Instances  will  be  encountered  where  a  reinforced  spread  foundation  on  weak  soils 
of  this  kind  would  be  more  practical  and  economical  than  going  down  to  greater 
depth  for  a  more  solid  soil.  Here  the  spread  foundation  may  be  made  of  such 
dimensions  that  the  soil  pressure  is  reduced  to  as  low  as  I  ton  per  square  foot. 
(See  Fig.  51.  page  85.) 

Sand  if  confined  and  dry  is  almost  noncompressible  and  makes  an  excellent 
foundation.  However,  it  is  best  to  be  conservative  and  not  apply  a  load  of  more 
than  2  tons  per  square  foot. 

Compact  gravel  may  be  loaded  to  3  tons  per  square  foot. 

Hard  pan,  coarse  gravel  cemented  with  dry  clayr  may  be  loaded  to  3  tons  per 
square  foot. 

For  airy  soil  condition,  other  than  solid  bed  rock,  we  recommend  against  a 
loading  of  over  3]  ^  tons  per  square  foot. 

Solid  bed  rock  can  safely  carry  any  load  which  may  be  imposed  by  the 
chimney.  This  may  run  as  high  as  18  to  20  tons  per  square  foot.  If  the  rock 


81 


lies  at  an  angle  the  slope  should  be  cut  into  steps  to  prevent  the  concrete  mass 
from  sliding.  The  surface  of  the  rock  should  be  thoroughly  cleaned  and  dis¬ 
integrated  soft  portions  removed.  The  surface  should  be  thoroughly  wetted  down 
before  placing  the  first  layer  of  concrete.  (See  design,  page  85,  Fig.  44.) 

In  the  case  of  spread  foundations,  precautions  should  be  taken  to  ascertain  if 
the  soil  encountered  in  the  bottom  of  the  excavation  continues  the  same  for  a 
considerable  depth.  It  should  be  made  certain  that  the  hard  strata  encountered 
is  not  a  thin  strata  overlying  a  soft  one,  such  as  cpiicksand,  soft,  wet,  silty  clay  or 
wet  muck. 

The  bearing  capacity  of  the  soil  may  be  determined  by  driving  down  an  iron 
rod,  making  borings  with  a  soil  auger,  sinking  a  hollow  pipe  by  means  of  a 
water  jet,  or  by  applying  a  test  load  on  a  mast  and  recording  the  settlement. 
Holes  may  be  dug  at  several  points  in  the  foundation.  In  general  should  the  same 
or  better  soil  be  encountered  through  a  depth  of  8  or  10  feet,  the  foundation  soil 
may  be  considered  safe  to  build  on. 

The  nature  of  the  soils  for  a  considerable  depth  in  the  vicinity  of  the  founda¬ 
tion  may  often  be  determined  by  observing  nearby  excavations  or  by  records  of 
foundations  supporting  other  structures  in  the  neighborhood. 

On  page  85  are  illustrations  of  several  different  designs  of  the  most  common 
foundations  (Fig.  42).  They  are  built  of  concrete,  made  of  a  mixture  of  one 
part  by  volume  of  Portland  cement,  three  parts  coarse  clean  sharp  sand  and  five 
parts  crushed  234-inch  graded  concrete  stone  or  suitable  gravel.  We  recommend 
the  American  Society  of  Civil  Engineers’  specifications  for  the  proportioning, 
mixing  and  laying  of  mass  concrete. 

The  table  on  page  80.  is  given  to  enable  the  Engineer  or  Architect  to  make  his 
approximate  preliminary  layout,  and  should  not  be  taken  as  final  in  all  cases. 
The  exact  pressure  should  be  calculated  and  the  foundation  determined  for  the 
particular  size  and  design  of  chimney,  for  the  reason  that  a  chimney  of  the  same 
height  and  diameter  may  vary  in  weight  according  to  the  type,  the  lining  and 
other  specifications. 

Where  the  necessary  depth  of  excavation  to  firm  soil  is  greater  than  the 
required  thickness  of  the  concrete  foundation  to  safely  resist  shear  and  bending 
yet  not  deep  enough  to  make  piling  imperative,  a  foundation  with  a  sub-base  and 
earth  fill  is  the  most  economical.  (See  page  85,  Figs.  47-48-49-50.) 

We  call  attention  to  the  drawing  of  the  reinforced  spread  foundation  where 
the  thickness  is  materially  reduced.  This  type  may  be  used  when  deeper  excava¬ 
tions  are  expensive  and  the  cost  of  sheet  piling,  pumping  or  cribbing  is  more  than 
the  additional  cost  of  steel  reinforcement.  The  steel  should  be  designed  to  resist 
the  shear  or  bending  that  may  occur  in  the  thin  slab  of  concrete. 

When  a  chimney  foundation  is  built  adjacent  to  a  building  wall  we  recommend, 
if  possible,  there  be  no  connection  between  it  and  the  wall  footings.  The  chimney 
footings  for  the  chimney  should  be  carried  down  to  at  least  the  depth  of  the  wall 
footings. 


82 


Underground  flues  are  not  uncommon.  A  design  of  this  type  is  illustrated 
by  a  typical  drawing  (page  85,  Fig.  50).  This  condition  occurs  where  the  boiler 
room  floor  is  some  distance  below  ground  or  where  the  chimney  is  used  in  con¬ 
nection  with  brass  f  urnaces  or  similar  melting  furnaces. 

A  unique  solution  of  a  chimney  foundation  is  shown  in  Fig.  43  on  page  85. 

The  chimney  was  built  adjacent  to  a  stone  quarry  where  continued  heavy 
blasting  is  carried  on.  This  subjected  the  chimney  to  two  forms  of  shock  other 
than  wind  shock. 

First — The  concussion  waves  through  the  ether  from  the  explosions.  Second — - 
The  shock  carried  through  the  underlying  rock  to  the  foundation.  The  former 
was  easily  met  by  an  extra  heavy  column  design.  The  latter  was  more  of  a 
problem  and  was  solved  in  the  following  manner: 

An  excavation  18'  3"  square  and  6'  deep  was  made  in  the  solid  rock.  This 
was  lined  on  the  bottom  and  four  sides  with  12"  of  concrete  in  which  were  imbedded 
steel  rods.  In  this  concrete  box  was  laid  clay  24"  thick,  tamped  hard  in  separate 
thin  layers.  This  formed  a  clay  cushion  upon  which  the  concrete  chimney  founda¬ 
tion  was  constructed. 

Between  the  sides  of  the  chimney  foundation  and  sides  of  the  concrete  box  a 
l1  2  joint  was  left  and  filled  with  asphalt.  In  this  manner  the  clay  cushion  was 
absolutely  confined  within  the  concrete  walls. 

The  chimney  has  stood  for  years,  withstanding  the  shocks  from  the  blasting. 

By  their  long  and  varied  experience  the  Engineers  of  the  Custodis  Com¬ 
pany  are  prepared  to  solve  any  chimney  foundation  problem,  no  matter  how  diffi¬ 
cult  or  baffling. 


PILE  FOUNDATIONS 

Where  soft  unreliable  soil,  such  as  quicksand,  wet  clay  and  harbor  muck 
is  encountered  piles  are  frequently  found  necessary. 

There  are  tw  o  classes  of  piles  in  common  use,  w  ood  piles  and  concrete  piles. 

Wood  piles  are  more  frequently  used.  They  are  very  satisfactory  if  installed 
so  that  they  are  always  wet  and  are  protected  against  attacks  of  the  marine  borers. 
It  is  highly  important  that  wood  piles  be  cut  off  so  that  they  w  ill  always  be  sat¬ 
urated  or  submerged.  In  determining  the  point  of  cut  off  consideration  should 
be  given  to  possible  future  lowering  of  the  water  level. 

Concrete  piles  have  several  advantages  over  wood  piles — among  which  are 
immunity  from  decay  and  greater  bearing  capacity  and  in  some  cases  lower 
first  cost  than  wood  piles.  There  are  two  general  types  of  concrete  piles:  first,  the 
“cast  in  place”  pile;  and  second  the  “pre  cast”  pile.  Ordinarily  “cast  in  place” 
piles  are  not  reinforced  while  “pre  cast”  piles  are  reinforced  so  that  they  can  be 
handled. 

Piles  carry  their  load  partly  by  friction  with  the  earth  throughout  its  length 


83 


and  partly  as  a  column  supported  at  its  lower  end  by  being  firmly  driven  into 
stable  soil,  or  upon  rock. 

Piles  are  driven  by  means  of  a  pile  driver  or  in*  sandy  soils  are  sunk  by 
means  of  a  water  jet. 

The  carrying  capacity  of  piles  is  ordinarily  determined  by  means  of  the 
“Engineering  News  Formula 


L  =  ‘  - 

S  +c 


Where  L  =  Load  in  pounds 

w=  Weight  of  falling  parts  in  pounds 
h  =  Drop  in  feet  of  falling  parts 
S  =  Final  penetration  per  blow  in  inches 

c=  Constant  whose  value  is  1.0  for  gravity  hammers  and  0.1  for 
steam  hammers. 

If  in  doubt  as  to  the  carrying  capacity  of  the  piles  a  test  load  can  be  applied. 

For  ordinary  conditions  a  maximum  load  of  15  tons  per  pile  for  wood  piles, 
and  30  tons  per  pile  for  the  standard  “cast  in  place”  concrete  piles  is  recommended. 

In  view  of  the  widely  varying  soil  conditions  no  hard  and  fast  rule  can  be 
given.  e,  therefore,  suggest  that  conference  be  arranged  with  our  engineers  so 
that  we  may  make  a  report  based  upon  a  study  of  the  conditions. 

Wood  piles  are  ordinarily  spaced  approximately  2'  6"  to  3'  0"  center  to  center 
and  project  6"  into  the  cap  \\  hile  standard  “cast  in  place"  concrete  piles  are  spaced 
3'  0"  center  to  center  and  project  3"  into  the  cap. 

Illustrations  of  some  types  of  pile  foundations  are  given  (page  85,  Figs.  45, 
46).  Note  that  the  designs  of  the  concrete  mass  overlying  the  piles  are  similar 
to  the  concrete  footings  employed  in  cases  where  the  foundations  rest  directly 
upon  the  soils. 


84 


LUXJ 

r  I  .  i  .  j 


lZ,  I  -i-t 


m  Wcm  DJ 


Fig.  42 

Typical  designs  of  mass 
concrete  foundations 


Z7 

1 

zz 

u 

r 

'•  2Z 

34 

e>. 

&  Oc 

t 

W  Z. 

Earth 

F.ll 

p  Oa 

iz 

2?i 

T\ 

V- 

i  ,  f-r  r-r~ 

Live  Bed  Rock 


Fig.  44 

Foundations  resting  on 
solid  rock 


Fig.  43 

Unique  design  of  a  chimney  foundation 
to  resist  shocks  from  blasting  in  an 
adjacent  stone  quarry.  Showing  con¬ 
fined  artificial  clay  cushion.  See 
next  page 


Fig.  16 

Reinforced  spread  built 
for  foundations  on  piling 


Fig.  49 

Designs  of  foundations  with 
concrete  sub-base  under¬ 
ground.  Note  earth  fill  in 
center  covered  over  with 
concrete  floor 


Fig.  50 

Typical  design  of  foundation 
with  underground  flue 


Design  of  a  shallow .  reinforced  concrete 
foundation  for  a  chimney  450'  x  16' 


85 


CHAPTER  VI 
LIGHTNING  RODS 


Renjamin  Franklin  installed  the  first  lightning 
rod  on  his  own  house  in  1753,  after  making  careful 
researches.  In  the  United  States  and  France 
public  approval  was  quickly  given  his  invention. 
In  Europe,  generally  speaking,  the  installation  of 
lightning  rods  was  opposed  on  t  lie  grounds  that  they 
interfered  with  Divine  punishment  of  the  wicked. 

A  half  century  or  so  ago  unscrupulous  and 
unskilled  men  took  up  the  business  of  selling  and 
installing  lightning  rods.  Their  equipment  was 
cheap,  flimsy  and  unscientific.  Their  business 
methods  were  questionable  and  frequently  dis¬ 
honest.  The  natural  result  was  that  lightning 
protection  was  looked  upon  with  disfavor  and 
suspicion,  and  in  fact  today,  some  of  this  feeling 
still  exists. 

During  the  past  few  years  the  Insurance 
Companies  have  kept  careful  records  of  the  fire 
losses  caused  by  lightning.  They  have  found  that 
these  losses  average  over  eight  million  dollars 
yearly,  also  that  in  the  case  of  barns,  lightning 
rods  properly  installed  are  99%  efficient,  and  in 
the  case  of  other  structures  the  efficiency  is  but 
little  below  that  point. 

As  a  result  of  the  statistics  now  available,  the 
Rureau  of  Standards,  Washington,  D.  C.,  and 
many  scientific  bodies  in  the  United  States  and 
Europe  have  endorsed  the  use  of  lightning  rods. 
In  fact  educated  thought  throughout  the  world 
favors  this  protection  against  lightning. 

For  a  number  of  years  the  Custodis  Com¬ 
pany  has  kept  records  of  the  chimneys  damaged  by 
lightning,  that  have  come  under  their  observation. 
On  account  of  being  the  oldest  Chimney 
Company  in  the  country  operating  over 
the  entire  continent  of  North  America,  more  cases 
of  chimneys  struck  by  lightning  are  reported  to  this 
Company  than  to  any  other  firm.  Our  files  show 
that  we  have  never  been  called  upon  to  repair  a 
chimney  seriously  damaged  by  lightning  that  was 
equipped  with  a  lightning  rod  properly  designed  and 


Encircling 

Cable 


>r:  i 

i 

© 

§ 

Detail  of  connec¬ 
tion  showing  cop¬ 
per  bronze  T  at 
point  of  juncture 
with  conductor 
cable 


- --p- _ /?^> 


Detail  of 
Cable  Clamp 


Elevation  Showing 
Arrangement  of 
Lightning  Rods 


86 


installed.  In  several  cases  we  have  repaired  the  aerial  terminals  or  points  of 
lightning  rods  which  have  carried  off  heavy  discharges  and  found  that  chimney 
was  undamaged. 

The  damage  to  some  chimneys  was  so  severe  that  the  plant  was  forced  to 
suspend  operations,  causing  a  heavy  loss.  The  cost  of  adequate  lightning  pro¬ 
tection  is  small.  It  is  unquestioned  that  it  is  good  insurance  at  a  low  rate.  The 
installation  of  such  protection  warrants  the  most  serious  consideration  by  every 
owner,  architect  and  engineer. 

Lightning  is  the  name  given  to  the  discharge  of  electrical  energy  from  the 
clouds,  the  difference  in  potential  being  sufficient  to  overcome  the  resistance  of 
the  intervening  gaps.  The  resistance  through  the  air  between  charged  clouds  and 
tall  structures  is  generally  less  than  the  resistance  between  the  charged  clouds 
and  the  earth.  For  that  reason  tall  structures  are  generally  damaged  by  the 
passage  of  the  electrical  discharge,  unless  a  path  in  the  form  of  a  lightning  rod  is 
provided  to  the  ground. 

There  are  usually  several  discharges.  The  first  warms  the  air  in  the  path  of 
the  discharge  decreasing  its  resistance  so  that  the  remaining  discharges  will  take 
place  along  the  same  path,  provided  the  warm  air  column  is  not  moved  laterally 
by  the  wind.  Experience  has  shown  that  this  movement  is  extremely  likely  to 
occur.  Provision  is,  therefore,  made  accordingly  by  installing  several  air  terminals 
properly  distributed  on  the  structure  to  be  protected. 

There  is  no  exact  data  available  regarding  the  electrical  characteristics 
of  lightning.  There  is  no  doubt  that  the  currents  in  flashes  must  be  reckoned  in 
the  thousands  of  amperes  and  millions  of  volts  with  a  frequency  in  the  thousands 
of  cycles. 

This  lack  of  information  accounts  for  the  difference  of  opinion  among  the 
scientists  as  to  what  is  adequate  protection.  Some  manufacturers  of  lightning 
rods  are  tempted  to  take  advantage  of  this  by  producing  weird  and  complicated 
systems  that  do  little  else  than  increase  the  cost. 

The  Custodis  Company  has  for  many  years  investigated  the  subject  and 
concludes  as  follows: 

The  interest  of  its  clients  is  served  best  when  the  lightning  rod  is  installed  as 
the  chimney  is  built. 

The  “Contour"  system  consisting  of  a  network  of  conductors  is  designed  upon 
the  theory  that  it  is  better  to  depend  upon  a  large  number  of  small  conductors 
rather  than  one  or  two  large  conductors  as  is  the  case  of  the  “Point"  system.  Experi¬ 
ence  has  shown  that  the  “Contour"  system  is  not  more  effective  in  discharging 
electrical  energy  than  the  “Point"  system  and  neither  is  it  more  reliable.  The  former 
is  more  complicated  than  the  latter  system.  We  recommend  the  “Point  system. 

Iron  conductors  are  slightly  superior  from  an  electrical  standpoint  and  are 
cheaper  in  first  cost:  however,  copper  resists  corrosion  better  and  is  more  workable, 
in  the  field.  These  are  the  governing  factors  and  the  use  of  copper  has  become 
practically  universal. 


87 


The  aerial  terminals  or  points  should  be  heavy  and  substantial  to  maintain 
their  vertical  position.  They  should  have  sufficient  cross  section  to  prevent  their 
fusing  when  carrying  a  heavy  discharge.  We  recommend  solid  copper  rods  at 
least  34  inches  in  diameter.  6]<?  feet  long.  It  is  good  practice  to  tip  the  extreme 
point  with  platinum  as  that  metal  better  resists  corrosion  and  has  a  much  higher 
fusing  point. 

The  points  should  project  above  the  top  of  the  chimney  to  divert  the  discharge 
from  the  warm  smoke  column  to  the  points.  When  a  cast  iron  cap  or  any  metal 
ornament  is  used  on  a  chimney  there  should  be  a  connection  between  it  and  the 
system  of  lightning  protection. 

The  number  of  points  necessary  depends  upon  the  diameter  of  the  chimney 
at  the  top.  Authorities  differ  as  to  the  spacing  but  our  experience  has  been  that 
good  results  are  obtained  from  the  following  spacing: 


Diameter  up  to  1  feet 

1  point 

From  1  feet  to  6  feet 

2  points 

From  6  feet  to  8  feet 

.3  points 

From  8  feet  to  13  feet 

1  points 

From  13  feet  to  16  feet . 

5  points 

The  points  at  the  top  should  he  anchored  to  the  masonry  with  extra  heavy 
clamp  anchors  to  insure  their  being  in  proper  position  at  all  times. 

The  conductors  or  downleading  cables  are  fastened  to  the  side  of  the  chimney 
by  means  of  similar  clamps  spaced  approximately  6  feet  center  to  center,  see 
illustration  page  86.  The  point  and  cable  anchors  are  made  of  copper  bronze  to 
avoid  electrolytic  action.  Great  care  should  be  taken  to  secure  good  electrical 
contact  in  all  connections. 

Various  forms  of  conductors  or  downleading  cables  have  been  proposed,  many 
of  unusual  form,  however,  most  of  the  claimed  advantages  are  non-existent,  t  he 
tightly  woven  seven  strand  four  wire  No.  11  BAS  gauge  soft  copper  cable  which 
we  use  as  a  downleading  cable  has  a  small  amount  of  surface  exposed  to  corrosion. 
It  has  no  tendency  to  sag  or  be  pulled  out  of  shape  and  from  an  electrical  stand¬ 
point  is  the  equal  of  the  so-called  tubular  cable  which  is  deficient  in  the  first  men¬ 
tioned  qualities.  \\  e  recommend  more  than  one  downleading  cable  for  chimneys 
of  large  diameter. 

Good  ground  connections  are  important  if  the  lightning  rod  is  to  function 
properly.  The  end  should  be  buried  in  soil  that  is  always  moist.  One  of  the  best 
grounds  is  an  underground  waterpipe.  If  this  is  not  possible  to  secure  the  end  can 
be  coiled  to  form  a  ground  plate  or  a  copper  ground  plate  may  be  used. 

There  have  been  many  specifications  prepared  bv  various  insurance  bureaus, 
state  and  government  authorities.  All  of  these  vary  somewhat  and  some  of  them 
provide  for  a  most  elaborate  system.  Based  upon  many  years'  experience,  our 
opinion  is  that  the  lightning  rod  above  described  and  illustrated  on  page  86  pro¬ 
vides  good  protection.  We  are,  however,  at  all  times  ready  to  cooperate  with  the 
engineer  or  architect  in  the  working  out  of  any  design  which  he  may  favor. 


88 


NOTES  ON  CARE  OF  CHIMNEYS 

Before  putting-  a  brick  chimney  in  service,  the  walls  should  be  thoroughly 
dried  out.  This  should  be  done  gradually.  Treat  the  chimney  in  the  same  manner 
as  you  would  treat  the  brickwork  of  a  boiler  setting  or  an  industrial  furnace. 
It  should  not  be  be  suddenly  subjected  to  high  temperatures,  for  unequal  expan¬ 
sion  is  liable  to  take  place,  or  the  moisture  in  the  brick  work  may  be  converted 
into  steam,  tending  to  crack  the  walls. 

If  the  heat  is  gradually  applied,  the  brickwork  will  have  time  to  adjust  itself 
and  equalize  any  unequal  expansion  so  that  there  are  no  detrimental  results. 

In  a  new  plant  where  new  boilers  and  furnaces  are  being  installed  as  well  as 
a  new  chimney,  slow  fires  will  naturally  be  built.  The  heat  from  these  will  be 
sufficient  to  dry  out  the  chimney. 

In  established  plants  where  only  a  new  chimney  is  installed  it  is  not  always 
practicable  to  put  a  slow  fire  under  the  boilers.  In  cases  of  this  kind  the  clean 
out  door  should  be  kept  open  to  allow  the  circulation  of  air.  We  also  recommend 
the  placing  of  salamanders  in  the  bottom  of  the  chimney  and  building  fires  in 
them  for  a  few  days.  Do  not  build  an  open  fire  in  the  bottom  of  the  chimney, 
either  to  dry  it  out  or  to  accelerate  draft  after  a  shutdown,  for  the  chimney  is 
not  designed  to  w  ithstand  such  treatment.  W  here  it  is  necessary  to  accelerate 
draft,  it  is  good  practice  to  provide  an  auxiliary  furnace  at  the  foot  of  the  chimney 
in  w  hich  a  f ire  may  be  maintained. 

It  is  important  that  the  chimney  be  cleaned  out  at  regular  intervals.  A  clean 
out  door  is  provided  for  that  purpose.  If  soot  and  cinders  are  allowed  to  collect 
in  the  bottom  the  accumulation  is  liable  to  ignite  and  burn  with  intense  heat  under 
certain  operating  conditions;  also  there  is  a  possibility  of  dust  explosions,  either  of 
which  may  damage  the  structure. 

W  hen  the  chimney  w  as  built  the  conditions  of  service  were  carefully  considered 
and  the  chimney  designed  accordingly.  Should  the  manufacturing  processes  or 
conditions  of  operation  change,  thereby  changing  the  flue  temperature  or  the 
chemical  analysis  of  the  gases,  the  builder  of  the  chimney  should  be  consulted 
regarding  the  advisability  of  any  alterations  which  may  be  necessary  to  enable 
the  chimney  to  successfully  meet  these  new  conditions.  Do  not  discharge  acid 
gases  into  a  chimney  designed  for  steam  boiler  service.  Consider  carefully  the  size 
and  capacity  of  the  chimney  before  adding  additional  boilers  or  apparatus  to  in¬ 
crease  the  overload  of  the  boilers. 

Where  oil  is  burned  as  fuel,  care  should  be  exercised  to  properly  regulate  the 
fuel  oil  burners,  to  prevent  combustible  material  or  gases  being  carried  over  into 
the  chimney  where  they  may  burn  or  explode. 


89 


STANDARD  SPECIFICATIONS  FOR  RADIAL  RRICK  CHIMNEY 

General  Conditions:  The  chimney  contractor  must  conform  to  all  State  Laws  and  corporate 
ordinances  which  apply  to  this  work. 

Bids  will  be  received  only  from  contractors  who  have  an  established  reputation  for  building 
radial  brick  chimneys. 

The  contractor  shall  furnish  all  necessary  labor,  scaffolding,  tools  and  materials;  do  all  carting 
and  unloading  of  his  materials  and  equipment,  and  complete  the  chimney  ready  for  operation  in 
accordance  with  the  true  intent  and  meaning  of  the  drawings  and  specifications. 

The  work  shall  be  carried  on  at  all  times  under  the  supervision  of  a  competent  and  experienced 
Foreman. 

All  materials  shall  be  the  best  of  their  respective  kinds  and  the  work  shall  be  performed  in  a 
thorough  and  workmanlike  manner  to  the  satisfaction  of  the  owner  or  his  authorized  representative. 
The  contractor  shall  remove  all  rubbish  due  to  his  work. 

The  chimney  is  to  be  built  at . . . . 

(Name  of  Town  or  City,) 

There  is  a  siding  of  the  . . .  .  . Railroad  on  which  cars  may  be 

set  for  unloading.  The  wheeling  or  trucking  distance  to  the  chimney  site  from  the  siding  will  not 
exceed . feet. 

Unobstructed  access  will  be  provided  for  the  delivery  and  removal  of  materials  and  tools. 
There  will  be  sufficient  storage  room  and  space  at  the  site  of  the  chimney  for  proper  prosecution 
of  the  work. 

An  adequate  supply  of  water  will  be  provided  free  at  the  chimney  site,  but  the  contractor 
will  have  to  make  his  own  water  connections. 

Foundation:  The . . . shall  do  all  excavating  and  build  the  foundation  as 

shown  on  the  drawing  accompanying  these  specifications.  The  concrete  shall  be  composed  of  one 
part  Portland  cement,  three  parts  clean  sharp  sand  and  five  parts  2(4"  graded  concrete  stone  or 
suitable  gravel.  It  shall  be  mixed  and  deposited  in  accordance  with  the  specifications  of  the 
American  Society  of  Civil  Engineers. 

Design:  The  design  of  the  chimney  is  shown  on  the  accompanying  drawing. 

Height  of  chimney  above  top  of  foundation  . feet _ inches. 

Internal  diameter  at  top . feet... . inches. 

In  case  the  contractor's  standard  wall  thicknesses  are  not  as  shown  on  the  drawing,  samples 
of  brick  shall  be  submitted  and  a  reasonable  variation  given  consideration. 

Column:  The  column  shall  be  constructed  of  perforated  radial  brick,  built  true  to  taper  and 
plumb  to  center  throughout. 

Base  (If  Used):  The  base  of  the  chimney  shall  be  .  in  section,  as  shown  on 

drawing.  The  face  brick  shall  be .  backed  up  with  hard  burned  common 

brick,  laid  in  lime  cement  mortar  with  full  joints  as  herein  specified. 

Radial  Brick:  The  radial  brick  shall  be  manufactured  from  refractory  clay,  moulded  hollow' 
with  a  multiplicity  of  vertical  perforations,  which  perforations  shall  have  a  total  area  of  not  more 
than  25%  of  the  gross  cross  sectional  area  of  the  brick.  They  shall  be  shaped  so  that  when  laid 
in  place  the  ring  will  be  formed  with  radial  joints  not  over  Y%  in  thickness. 

The  faces  of  all  radial  brick  forming  the  external  surface  of  the  chimney  shall  be  smooth  and 
reasonably  uniform  in  size  and  color.  Care  should  be  taken  in  selecting  the  radial  lengths  of  the 
brick  in  order  to  secure  a  strong  bond. 

All  brick  shall  be  hard,  well  burned,  of  sound  ringing  quality,  weather  and  acid  proof.  The 
radial  brickwork  in  place  shall  weigh  not  less  than  120  lbs.  per  cubic  foot. 


!l 


90 


Lining:  A  perforated  radial  brick  expansion  lining  4"  thick  shall  be  provided,  starting  2' 

below  the  bottom  of  the  Hue  opening  and  extending  to  a  height  of .  feet.  An  air  space  is  to 

be  left  between  the  main  wall  and  the  lining  of  not  less  than  2".  Care  shall  be  exercised  to  keep 
the  air  space  free  from  debris  during  construction.  The  main  wall  is  to  be  racked  out  over  the 
lining  to  divert  the  falling  soot. 

Mortar:  Ail  brick  work  shall  be  laid  in  lime  cement  mortar,  consisting  of  Portland  cement, 
fresh  burned  lump  lime,  thoroughly  slacked,  and  clean  sharp  sand,  free  from  vegetable  matter,  loam 
or  other  impurities.  The  proportions  shall  be  one  part  Portland  cement,  two  parts  lime  and  five  parts 
sand.  The  lime  shall  be  thoroughly  slacked,  after  which  the  sand  shall  be  cut  through  the  lime  paste. 

The  cement  shall  be  added  to  the  lime  sand  paste  as  the  mortar  is  needed.  No  mortar  shall 
be  used  after  having  taken  an  initial  set  and  no  relempering  will  be  permitted. 

Bonding:  Common  brick  shall  be  laid  in  true  and  level  courses  in  a  full  bed  of  mortar  with  a 
header  course  every  sixth  course. 

Radial  brick  shall  be  laid  in  a  full  bed  of  mortar,  level,  plumb  and  true  to  circle.  The  radial 
brickwork  shall  be  bonded  every  third  course.  The  outside  joints  shall  be  neatly  struck. 

Fi.ue  Opening:  Build  in  the  chimney  a  flue  opening  where  shown  and  of  a  size  to  develop 

the  full  working  capacity  of  the  chimney.  The  opening  shall  be  approximately . feet  in  height 

and . feet  in  width  with  the  bottom  approximately _ feet  above  the  top  of  the  foundation. 

Heavy  steel  I-Beams  shall  be  placed  above  and  below  the  opening  as  shown  on  plan,  leaving  air 
spaces  at  each  end  for  expansion.  Internal  steel  bands,  3"x  34”,  shall  be  built  into  the  masonry 
above  and  below  the  opening. 

Ladders:  Step  irons,  spaced  approximately  20"  center  to  center,  shall  be  provided  inside  the 
chimney  to  form  a  ladder.  They  shall  be  made  of  one  piece  round  steel  bent  U-shape  and  12" 
wide.  The  ends  of  the  step  irons  entering  the  masonry  shall  be  turned  down  2"  into  the  brickwork. 
They  shall  be  painted  with  approved  paint. 

Reinforcing  Bands:  Steel  reinforcing  bands,  3"x  J4",  shall  be  built  into  the  chimney  where 
shown  on  the  drawing.  They  shall  be  thoroughly  imbedded  in  the  masonry. 

Head:  A  suitable  head  shall  be  built  by  corbeling  out  at  the  top  of  the  column.  The  top 
shall  be  protected  by  a  substantial  water  table  of  cement  mortar,  in  which  shall  be  set  a  suitable 
retaining  band  of  steel. 

Cleanout  Door:  Furnish  and  set  a  cast  iron  cleanout  door  and  frame  feet  by  feet 

at  the  bottom  of  the  chimney  where  indicated,  securely  anchored  to  the  brickwork. 

Lightning  Rod:  The  lightning  protection  will  consist  of . lengths  of  solid  copper  rod 

.  in  diameter  and . ...long  securely  supported  at  the  top  of  the  stack  by  means  of  sub¬ 
stantial  copper  bronze  braces  built  into  the  masonry  and  provided  with  clamps  to  grip  the  rod, 

and  will  be  connected  to  a  down  leading  cable  of . stranded  dead  soft  copper  cable  through  a 

heavy  copper  bronze  T  into  which  the  vertical  copper  rod  will  be  screwed  and  to  which  the  down 
leading  cable  will  be  electrically  connected.  This  down  leading  cable  will  be  secured  to  the  side 
of  the  chimney  by  means  of  copper  bronze  fasteners  spaced  not  over  6  feet  centers  and  will  ter¬ 
minate  in  a  coil  of  copper  cable  buried  in  the  earth. 

Where  more  than  two  points  are  used,  a  copper  cable  of  the  same  diameter  and  quality  as  the 
down  leading  cable  will  encircle  the  stack  under  the  head  and  will  be  held  in  place  by  copper  bronze 
clamps.  The  lower  ends  of  the  solid  copper  rods  will  he  connected  to  the  encircling  cable  through 
a  heavy  copper  bronze  T  into  which  the  vertical  rods  are  screwed  and  through  which  the  encircling 
cable  will  pass,  insuring  an  electrical  connection  between  the  vertical  point  and  the  encircling 
cable,  which  in  turn  will  be  connected  with  the  down  leading  cable  through  a  heavy  copper  bronze  T 
described  above. 

The  complete  system  will  be  constructed  and  put  together  in  a  substantial  manner  to  insure 
an  uninterrupted  circuit  from  the  tip  of  the  rod  to  the  ground. 


91 


Insurance:  The  contractor  shall  carry  at  his  own  expense  during  the  period  of  con¬ 
struction  employee’s  or  workman’s  compensation  and  public  liability  insurance  according  to  the 

Laws  of  the  State  of  _  The  Contractor  shall  furnish  a  certificate  of 

such  insurance. 

Guarantee:  The  contractor  shall  furnish  a  written  guarantee  that  the  chimney  is  of  proper 
design  and  workmanship,  capable  of  withstanding  a  wind  velocity  of  one  hundred  miles  per  hour, 
and  the  influence  of  the  atmosphere  and  internal  temperatures  due  to  dry  gases  not  exceeding 
800  degrees  Fahrenheit,  and  that  during  the  period  of  five  years  from  date  of  completion  he  will  re¬ 
pair,  free  of  charge,  any  defects  from  such  causes. 

Time  of  Completion:  Bids  shall  state  the  time  required  to  complete  the  chimney  after  receipt 
of  signed  contract  and  approved  drawings.  Drawings  for  approval  shall  be  submitted  within  ten 
(10)  days  from  date  of  signed  contract. 

The  following  information  shall  be  given: 

Name  and  address  of  the  manufacturer  of  the  brick. 

Location  of  the  brick  yard. 

A  list  of  chimneys  in  the  vicinity  of  the  proposed  operation  constructed  by  him  which  have 
been  in  successful  operation  for  at  least  live  (5)  years. 

The  chimney  shall  be  built  according  to  the  Alpl  ions  Custodis  Chimney  Construction  Company 
system  of  construction. 


92 


